I have seen plenty of barns with big feed bins do just that, topping them.
Don’t know how often they feed to the bottom and clean them out, probably often also.
When our vet told us to feed out of the sacks, for a while we were putting the whole sack inside the metal trash bins we were using, so we had the bags safe from anything that may want to get to them.
The past many years we keep the feed in a room nothing can get to them, so we have been feeding directly from the bags and works fine.
The bags do have some fines at the bottom, easy to discard when you get to them, they don’t get dumped in the containers like when we transferred the feed to them.
When feeding from sacks directly, you don’t have to clean bins any more.
If feed is fine in the sacks until fed, it should be fine while feeding off them.
I would say it depends how fast someone is going thru sacks how fresh that feed will stay.
Just more to consider, makes sense for us to do it as our vet suggested.