Using a Forge 1.21.1 server and breaking blocks with 2 hands causes blocks to take longer to break/drop. Same thing also happens when breaking a block one handed very fast.

take longer compared to what?
singleplayer, or older versions

take longer compared to what? singleplayer, or older versions

I haven't tried it in singleplayer but to give more clarification I break a block with both my actual hands, not by holding the trigger and it sits there for about 3 seconds and then disappears and drops the block on the ground.

could be that they added a minumum breakage time on the server or something
can you check if the time from when you start till it drops, is roughly equal to breaking it with the trigger?

yeah I'm more innterested of the time comparison, but I can check that myself I guess

I've tried the trigger and it breaks as normal and doesn't fake break like described, if breaking with one hand at a normal pace it breaks normally as well.

need to dig into the code, if I can remove that, maybe not possible

yeah, looks like that happens when breaking it faster than vanilla

I can upload a comparison, trying in survival yields the same results as the server.

yeah that looks like it just waits the vanilla time, before actually braking

Probably vanilla's server-side anti-cheat checks.