for the former case it is broken when you have devices/listeners with #IGMP v1/v2 or #MLD v1, instead of IGMPv3 / MLDv2. The issue you'll then potentially run into is IGMP / MLD report suppression. The big thing which #RFC4541 specifies an ugly workaround for... this whole report suppression has lead to so many hard to debug, subtle breakages for decades and now seems to continue with #Linux #DSA / #switchdev...
#multicast #igmpsnooping #mldsnooping