Select Tag Block seems to only work when sitting on the start tag (or in text following the start tag but before some other nested tag).
Select Tag Block should work anywhere (selecting the smallest encompassing tag block to make it unambiguous) - including if the cursor is on a closing tag.
Select Tag Content seems to select whatever is between ">" and "<" characters, regardless of the actual tags those characters are part of - in other words, Select Tag Content will not select nested tags, which seems like the behavior it should have (but maybe I 'm misunderstanding the intent of this command). In my opinion, this should also work if the cursor is on the closing tag.
Finally, something that's really a feature request: a command to jump to a matching tag would be very useful - similar to the "Match Bracket" command, but for tags.
Thanks for listening!