Is the number of empty wallets of a cryptocurrency a useful metric in any way?
I would say yes, at least to the extent that owners are aware that they exist and potentially become more likely to use.
It's roughly similar to Brave's userbase, though Brave is opt-in. Figures from 2020 put both in the low tens of millions.
MobileCoin is not a cryptocurrency.
The Wired article that the CEO of Mobilecoin is implicitly endorsing in this thread specifically categorizes Mobilecoin as a cryptocurrency. At least, it doesn’t seem to be a distinction worth splitting hairs about (yet).
I don't give a shit about Wired categorization. MobileCoin is a company. It has a fucking CEO. Cryptocurrency is by definition decentralized.
That particular ship has sailed. Much like people calling cryptocurrency "crypto", it's windmills all the way.