Looking at the neoforge changelog, my guess would be the change in .13

• 21.0.13 Adds an extension method to items (adjustAttributeModifiers) to allow modifying the exposed attributes (#1116)

yeah. I have that fixed in Dev but haven't rolled out a release yet. NeoForge is still in that initial release phase where things are still permitted to be breaking. once that settles out and we have a non-beta build we should be stable