Yes I agree too.
I can see the possibility of arguing reasonably against all three items that tranquility, if defined as absence of anxiety, does not meet a strict definition of a "pleasure," if we consider pleasure to be a "positive experience."
But that kind of argument would be a word game where in my view you would want to specify why you were playing it and what you hoped to accomplish. I think most people in common conversation would consider "he is tranquil" would be a common-sense description of someone enjoying some pleasure (sleep, rest, relaxation, daydreaming, etc.)
So maybe the real issue here is that confusion (or manipulation) arisese when people slide back and forth between (1) common sense discussion and (2) academic word-splitting without being clear what they are doing and trying to accomplish.
The whole question of talking about "highest pleasure" sets off alarm bells in my mind because how can that discussion really have any meaning without combining it with all sorts of other qualifying terms that explain the context in which you're talking.
It's kind of like waving a globe at someone and screaming "THIS IS THE WORLD" over and over and over.
Yes, it's a representation of the world, but it's not equivalent to the world in every respect. In most cases that kind of observation goes without saying, but not always. Is the person shouting "THIS IS THE WORLD" crazy? Or are they in the middle of a legitimate but heated discussion about the best way to draw maps and theories of cartography? The context of a discussion can determine whether what the people are saying is brilliant, or insane.