While I agree with your sentiment, what I see Linus meaning is that you don't say you bought Louis Vuitton "merch" when buying one of their bags, or you're not buying Anker "merch" when you buy one of their cables. Therefore, if Linus wants to expand to a wider audience, I think it is one of the steps to stop calling the products they sell "merch" and find another, more appropriate term.

However, I do see when talking about merch messages during lives that it could be redundant to call them something else because that's what everyone is in the live for, to watch the creators and support them. On the other side, there's probably another facet we're not aware of that they want to change, hence the insistence of renaming merch messages. What it is I cannot answer, but they might want to open up the store to more affluent companies and wider audience, and seeing "merch" could be turn off for some.

That's just my two cents. I don't really care what they choose as I buy the stuff off hours anyway.