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Alright, I just want make what is and isn't "reliable recovery" clear to those that aren't talking out of their ass and genuinely don't know. Basically, reliable recovery is a move or ability that guarantees you'll recover a set amount of your health everytime that you use it. Recover, Roost, Regenerator, Soft-Boiled, etc are reliable because you are ALWAYS going to recover the exact same amount of health everytime that you use it and barring moves like Taunt, nothing will prevent you from using them/having them be weaker.
Unreliable recovery moves, like Synthesis and Leech Seed, are moves that can be more easily negated or weakened. Synthesis has low PP and is countered by 3/4 weathers while Leech Seed doesn't work on Grass Types, MG or otherwise immune mons, and is removed upon switching.
That's not to say these moves are useless, they just aren't dependable enough to be considered reliable recovery.