I am PUP99 and have had <pethpp> and <petmpp> in my macros for a long time.
As of this week, when Pet's HP is at 100% i get that. When its MP is 100%, the macro reads out 0%.
Let the automaton use a spell and the macro then reads 98% (or such) correctly.
When it gets back up to 100% full pet MP, the <petmpp> macro displays 0% again.