Can you still skip levels by gaining a lot of XP?

Hello,

I recently saw a few speedrunning videos where people speedrun level 100 on a new profile with all the XP boosts possible.

After reaching a certain level, they try to get as close to the next level as possible and then set their XP gain to zero to gain a large amount of XP (e.g. via forgery) at once while leveling up. Doing this seemed to somehow grant a lot more XP and was what made these speedruns possible.

I was wondering if this was theoretically still possible or if this was patched, since I couldn't really find any information regarding how exactly the "exploit" worked and if it was ever fixed.

If you know, I would be very curious since I want to see what a speedrun after rekindled would look like and maybe try (especially because they are removing quest reqs for low level dungeons).

Thank you!