Well from the (incomplete, as turned out) info I gathered it turned out that it was never standardised to begin with (unlike meta description, for example), so it did not even have to be "deprecated". (Like it ever meant something in the real world…) I am definitely for any obsolete mischief, so it brings me joy hearing there is vernacular continuity!

(As for external search engines,FWIR, in its heyday some search engines briefly regarded it quite respectfully, but eventually due to SEO spam they either started to ignore it, or took it as a negative signal, allegedly. But as pointed out in sibling comment, it still survives in Yandex, what is quite surprising plot twist for me.)