I like it for a couple of reasons. For one thing, the way Snoke was cast aside so easily in TLJ warrants an explanation for his origins that is equally mundane - such as being a puppet (with the red curtains in his throne room to match). For another, we know Anakin’s ghost is fully detached from Vader. Therefore, there is nobody who could be speaking to Kylo through that mask besides Palpatine. Now, sure, you could make the argument that he never actually saw or heard anything, treating it more like an inanimate idol. But then we have to explain why he is seeing something now for the first time, which we simply don’t have the time for.

I think the reason Kylo goes to the mask is simply because Palpatine is a notorious liar. He wants to make sure he’s telling the truth about his beloved grandfather. Perhaps even let out his rage at Palpatine through it. Which is, of course, what he does by killing “Vader”. It doesn’t need to be more complicated than that.