So that sounds like one of two things - there are mods and features within mods that are designed to help with tree-felling specifically, however if that trick also works for other types of blocks too, that’s caused by something like Ore Excavator - a mod designed so that by holding down a key while breaking something (usually Tilde ~ ) all connected blocks of the same type break too. So the key issue is whether a mod like that exists in the pack you’re playing - if it does, you need to find the correct key, which should be listed in the controls. Skyfactory 4 is one skyblock pack that has it.