i may well be an outlier - though i don't think i'm entirely alone in this - but seeing complaints about not being able to get notifications when people share their posts that they themselves shared from someone else feels kinda bizarre to me.
(disclaimer: i'm not trying to shit on anyone's social media habits here; i just felt like sharing my own perspective)
like idk, coming from twitter, seeing mutuals retweet my retweets has always felt "good", sure. but other than that, qrts (i.e. actual interaction, with my own tweets specifically) have been all i've really cared about wrt retweets.
a retweet from someone i follow, that i then retweeted from them, getting retweeted by someone i don't know? i mean that's neat i guess, but i've never cared that much about being notified for it, y'know? to me it's like, "this person that i don't know liked/shared that other person's post that someone i follow happened to share". like i'm just personally so detached from the interaction that, generally, the notification really has felt like whatever - and that's (usually) extended to the person retweeting it as well. it's just that impersonal to me, and i guess my attitude has generally been just "well it's not my post; why should i care about who retweeted it?"
(whether that's a healthy way of thinking when using social media or not is a whole 'nother topic of its own)
again, this is just my own account on this; i have no wisdom to share here.
maybe people just have different habits/attitudes when it comes to social media. or maybe it's just me. i dunno. but i've always thought of seeing posts shared by people i follow as one of the main ways to find new people to follow; notifications being more like an afterthought in that regard.