When you implemented XP drops from ores, it is doing it for things that can be recraftrd (meteor cobble, broken meteor) and for ores that can drop themselves when mined (general ores) instead of just having it exclusive for certain ores that drop fragments of resources like fluorite, combat, sulfur, etc.

As it stands this allows for an infinite XP exploit.

When fixing this, please ensure also that ores that should be dropping exp cannot drop it when mined with silk touch

They can still decay, I think. If you remove a log.

I think what I'm thinking of is either a mechanic or an old bug

I think in order todo that you either need a unique block that only gens in the world that
Can drop it while the mined one is different that dosent or you need todo what they did in newer versions and have it just drop a fragment of it.

The issue here is that if you do the second thing you need to ensure xp dosent drop when you use silk touch.

ATM to keep things fair for what I'm doing I'm overwriting the xp drops on blocks that shouldn't using CraftTewaker to alter what happens when these blocks are broken

If you want it I can proide y'all the script; it will also include a few other misc things like breaking decos without silk drops nuggets as scrap (great for making structures not give you a mega resource advantage) and adding hazard gasses (coal & as absbestos mainly) to other modded blocks that should have it.

Or make it so only naturally generated ones drop XP's, just like how leaves placed down by players doesn't decay

Fixed it - will be in next update

The main things that should be known is the or that drop themselves as or blocks drop experience while they shouldn't along with oil deposits, for whatever reason