Hi... that's very impressive with the training. I'm a new budgie owner ( 3 months ), and I can understand how you're wondering, and I asked the same question....and lots of great advice in this thread (& most definitely on this entire forum.)
What I can tell you, looking back, as a new budgie owner.... as Therm, Aluz and FaeryBee all mentioned... it's all about time, going slow, and going at the budgie's pace and not yours.
Once I stopped "pushing" my budgie and realized it was about where we were in 6 months vs. 6 weeks, it was much better. I realized... it's not a race per se where one is trying to get to the finish line the fastest.
I found rushing things is very bad. It's bad for the bird and it's bad for the owner. And it's not even necessary. (And not for the best...!)
Someone who has great relationships with her budgies wrote: "slow and steady." No truer words have been spoken.
I found personally that there are good days and there are bad days, and sometimes you take two steps forward and one step back. But it's definitely a long haul (in it for the long haul); and there's no deadline.
My budgie went from looking at me like I might make him my dinner...(clearly uncomfortable) to now... we are friends. ... Is he the most "affectionate" budgie in the world? Not really. That's not his personality. He doesn't bob his head with glee every time I come to see him (although he might once in a blue moon, he's done that maybe twice) ... and some budgies will do that... I just don't think that's my bird's personality. (but it was well beyond 3 weeks that he showed joy at my arrival.)
Sometimes, if he's in the mood... he'll make a point to come to the corner of the cage where I visit him... to say hi. He's obviously coming over to say hello to me. That let's me know he wants to play. (but that doesn't even necessarily mean he wants to play with me. he might want to fly around. sometimes I let him out and he's off my hand in 30 seconds. And that's ok! I want him to feel that kind of freedom. I'm here to let him be him. *within reason of course. if he wants to be him by chewing my laptop cord... that's a no. I always keep a good eye on him when he's out of the cage.)
Sometimes, he does want to see me. He'll linger a little longer and that means he wants me to chat for a bit and engage him. But not for more than a few minutes. He has a short attention span.
It took him a long time to come fly to me on his own accord. Not long in the grand scheme of things, but not 4 weeks. He landed on my laptop, landed on my hand, landed on my phone... all of these incidents unexpected when they happened, and was well into things. A couple months. I let him be and then he was curious about what I
was up to. From my experience...I found the less you try to "force" a relationship with your budgie the more they trust you. (From my limited experience.)
Now, my budgie (Biz) will come land on me when he feels like saying hello (or when he wants a treat! lol
and it's not always for the treat. I can tell the difference and you will as well in time. Sometimes he's just curious and "dropping by." He'll chirp back to me when I speak to him... but that's if he wants to. You'll know in time. (and take your time.
There's definitely that personality factor and I don't think anyone knows for sure until many months into it, I think at least 4 - 6 months of being together. Some budgies are really affectionate (preen their owner's eyelashes, etc.) and others are more independent (like to go off and sing somewhere on their lonesome.) I think I have one that's in the middle.
One thing I found very helpful in the early days of having Biz was reading to him. He loved that! I calmly read the newspaper to him. (I would maybe recommend not the newspaper though. Maybe something more pleasant.
Budgies are very sensitive I think.)
He also loved classical music. There were times where I felt he was agitated, and when I put on classical (you can find it on youtube easily) ... he really calmed down.
Biz also stepped up on day 1... but I didn't go into all the training things you did, so we're going slow (he can come when called)... and also he was older... 4.5 months. If you have such a young budgie, time will tell on the personality, but given you have a youngster I think there is a decent chance for the potential that you're bonding.
My perspective would be to give it time, lots of time, and keep engaging in best practices and re-evaluate in a couple months, not a couple weeks. I'm not an expert, and that advice might be modified by an experienced moderator of this forum... so I should acknowledge that..... I guess what I'm saying is from my personal newbie experience, and what I've read.... slow, and low expectations. Let the budgie lead. I've found they will tell you what works and will lead the way on your relationship if you give them the chance and that's all about patience.
It really worked for me.