@brianleroux I was correct in my assumption of probably being wrong, some unattributed quotes from the #IndieWeb-dev channel correcting my assumptions
“i don't know of any microsub implementation (or reader of any kind) that supports sending or receiving webmentions.some micropub endpoints likely handle sending webmentions, but not receiving them.
“also websub is used to AVOID polling”
“And you still want to poll periodically to get missed updates like in case of momentary outages
Like I see it more as a mechanism to fast-track an update between polling intervals”