iNat is among other things a fancy field notebook. Field notebooks are indefensible and the starting point for countless more rigorous studies. It’s a great way to get georeferenced data on approximate ranges of species (with biases held in mind), phenology, sightings of new species, and it’s accessible to anyone to do somewhat more rigorous surveys if they want to. It’s by no means useless, it’s just important to understand what the data is and how it can or can’t be used. For some applied ecology and management purposes, random sampled data and intensive plots are less useful than iNat is.
I agree that ‘research grade’ isn’t a great term, maybe ‘community verified’ or ‘shared with partners’ would be better. ‘research’ is very broad and could mean anything and as others have pointed out, things that don’t count as ‘research grade’ on iNat may also be used for research.
It is what it is.