I'm not sure what you mean by "someone who wasn't exposed if added to the 40 man list b/c of COVID." Players don't get exposed to waivers when being added to the 40-man roster, ever. For the most part, assignment rules regarding the 40-man roster and the active roster (whether 30, 28, or 26-man depending on the date), haven't changed. An additional IL category (COVID-19) has been added, which functions like the 60-day IL (e.g., if you're on this IL, you're not counted against the 40-man).
Now, if you meant the 60-man player pool instead of the 40-man roster, then there are circumstances (we've discussed above) when a club can add a body to the player pool to replace a CV19-IL player, and subsequently remove that body without waivers when the CV19-IL player returns (the circumstance is that this option is only there if the club placed 3 or more players on the CV-IL on the same day). Other than that, if you add a body to the player pool to replace a player who goes on the CV-IL, you can't remove that body later without waivers. But we're talking about the pool, not the 40-man roster here. The rational thing for clubs to do, most of the time, is just allow the pool to be one body shorter - we're talking about 30 to 34 guys in addition to the active roster.
There's no circumstance under which you can add a player to the 40-man, and subsequently remove that player from the 40-man without exposing him to waivers. Just as as always been the case. You can still add the "best player not on the 40" - you can add an Alex Bohm. It's just that if you do, when Kingery comes off the CV-IL and you need a 40-man roster spot, you have to clear a spot. You don't do that by exposing Alec Bohm to waivers; you expose Robert Stock (or some other fungible reliever) - just as you would have done in 2019.