Token burn can come in different angles, that is, some project team burns tokens after their ICO, in this case, any unsold token left during the ICO is burnt thus reducing the supply, after which listing on exchanges takes place. On the other hand, some project team burn their tokens when already listed on exchanges to reduce the total supply while increasing the price.
However, burning a token when not listed on exchanges and when it is also clear the team didn't have any ICO do not really make sense on one hand as they should have set a total supply from the on set, but on the other hand, the team might have found out that in order to achieve their aim, then it will be worth it to burn off some tokens to reduce supply, in this case a better explanation will be made to the community.
In all ramifications, the essence of token burn is to have good token price, so if the team decides to do so before listing, I think it shouldn't be a problem so far they have a clear explanation on why they are doing so.