As I specifically noted, “the performance dates exist and are the same” - when all performance dates are the same, it can be reasonably inferred (i.e. it is probably but not certainly true) that the recording date was the same as the performance dates. Of course, it is possible that e.g. the backing track was on one date and the vocals on another, and if the recording date does not exist and backing track performance dates exist and are the same but the vocal performance dates are missing, then this inference will be incorrect - but in the absence of the missing information it is perhaps the best guess possible and is likely to be close.
(Of course, this would not be good enough as an algorithm in MusicBrainz itself, because MusicBrainz aims to be accurate and definitive. But when tagging, a best guess like this might well be better than having no recording date at all. And of course, it is quite possible to add an option to the plugin to turn such guesses on / off.)