I think we have a bit of a disconnect occuring.
I know you would have to take a receiver off of the field in order to insert a FB, I'm simply saying that coaches don't have any interest in doing so. I don't want to take Bailey off of the field to put in Mike Miller. You're limiting your offence by doing so, not adding a weapon.
And there may be an odd exception where your athletic FB/TE is a bigger weapon that your 3/4 receiver, but I think that's a case of not having good enough recievers.
Declan Cross had a couple seasons where he caught <2 passes a game, but the 2018 Argos won 4 games. Cross had 4 receptions this year and 0 rushing attempts. Those are FB numbers.
You're missing the point. Teams take receivers off to add another OL as well. They may do that at times on 2nd and short or 3rd and short for example or in the red zone. Weather may dictate a heavy lean towards the run game when a receiver is less important than an OL or FB blocking.
Calling him a FB or a RB is not really the point either.
Essentially a bigger / heavier Canadian that can block, play ST's and be an emergency RB as necessary.
Some FB or even OL have been used as receivers in these short down and distance situations. Calvin McCarthy would be another example.
I said this might only be used once or twice a game if and as necessary. Having a player that is actually capable of being a player for that role would be useful.
Previously I've asked whether Oliveria or Augustine were good blockers that could be used in those situations instead of a player like Miller.
You can't tell me a defence looking at A. Harris in the back field is not going to worry more about one of those two as well as A. Harris. More than Miller in that role.