CNAME cloaking is one of the more significant differences. It's typically used for tracking (and is becoming increasingly common), but also works for advertising. Instead of linking images/scripts/etc. to ads.advertisingcompany.com you can simply set up a CNAME under your TLD that points to the advertising company. Now the domain no longer appears in the blocklist, so all the requests (uploading tracking data, or downloading adverts/scripts) work just fine.

With MV2, uBlock is able to inspect the DNS record while it is vetting the request, thwarting this workaround.