Again, I don’t feel there is a constraint on the DM deeming an interaction is uncertain. The rules are incredibly permissive to the DM and basically don’t place any constraints on them at all, so I consider arguing about what the DM can or can’t do pretty pointless. The DM can do whatever they want.
However, I do not see anywhere in the rules that suggests the DM ought to suspend roleplaying in order to give the mechanics primacy in this circumstance. The rules don’t say the DM can’t or shouldn’t do so, just as they don’t say the DM can’t or shouldn’t do anything. But they don’t seem to say the DM should, and in fact, the statement that roleplaying is part of all aspects of the game would seem to indicate that suspending roleplaying is probably counter to the intent of the designers. If a DM decides to do so anyway (which the rules do permit), they are doing so of their own volition - which is to say, without the support of the rules.