Yes budgies wean faster, they also grow way faster. Phoenix is officially weaned as of Monday(has gone a whole week without formula) but he started denying formula when he was around 5-6weeks old (He's almost 8 weeks now).
How often are you feeding him the formula?
When Phoenix started weaning(I let him start on his own, he wanted to wean), I fed him formula 5 times a day (every four hours, this was when I had him start sleeping for 8 hours at night, I stopped feeding him formula at 10pm and woke up at 6am to feed him) then after a couple of days I started 4 times a day(about every 5-6hours) because he was wanting more real food instead of formula(I think it was around this time I had him start sleeping in the little travel-sized cage too, then after a couple more days 3 times a day (every 8 hours), and very quickly after this he was denying formula altogether, but I still started offering it twice a day(for only 3 days), then once a day(for only one day), just so he doesn't feel like I was starving him and to avoid him regressing back to formula.
Just be sure to offer plenty of solid food. You don't want to limit him during this time. Also, when he starts really flying he will lose some weight and that's okay, just be sure its not a sudden drop in weight, and also watch for any sign of lethargy or anything off about him.
I moved Phoenix to his normal-sized cage once he started flying around the room, but I put a soft nonpilling fleece blanket at the bottom in case he fell down.