I think with the Tracker, the response happens multiple times, once for each individual potential target. Its clearly not a single thing that happens in one instance and affects multiple targets at the same time.yeah, the main difference is that Silvan Tracker's response triggers whenever a Silvan character readies, not when the Tracker itself readies (although it does happen in the same window)
So you could pick and choose here to not fire the response for some potential targets.
this language means that every Silvan character readying creates an instance where you choose if you'll heal that character
if Wellinghall Preserver affected all Ents or if Silvan Tracker triggered once, it would be an all or nothing