How many other "Philip Cross"-like accounts are there on Wikipedia?

Well the place to look is here - https://archive.li/8xKkr
The archive of the top Wikipedia editors, where Mr Cross comes a miserable 308th with his 133,000 odd entries.

The Wikipedians at the top have edit counts in the millions and there are 1400 of these productive souls with edit counts over 50,000. It seems there are plenty of interested persons that take the Wikipedia world very seriously. Plenty of places for all manner of interest groups to operate from here. If there is just a single person behind any of the top 500 Wikipedian accounts I would be amazed.

The accounts to look at first would be those at the top with "AP" or "autopatrolled" status. You'll find a full explanation of this term in the Wikipedia but here is the effect:

New articles are normally noindexed (hidden from search engines) until they are patrolled. But when an autopatrolled user creates an article it is automatically marked as patrolled, and thus is immediately eligible for indexing by search engines.

Happy hunting.