Is it or is it not true that the attitude of many libertarians on the subject of abortion is:
"it's none of my business what somebody else does"
Depends on the libertarian. Much the same way as it depends on the conservative or liberal. I've noticed that people of all political stripes have this amazing ability to rationalize their views and (mis)behavior as they see necessary. Including conservatives.
I sense that you're looking for witches amongst the libertarian population to exorciate in much the same way that many look for witches amongst the democrat population to exorciate. I think that's self-defeating and counterproductive. Different people see things differently regardless of the political label they may be wearing.
What you say is true; however, I believe that the established Libertarian Party platform has been pro-abortion for some time.
There are people with agendas who look for openings all day everyday on this site to insert it into topics no matter how far fetched or off topic. This person has made another huge reach to introduce the hatred of freedom loving people into a thread about how people came to their senses about precious children sent to this earth by God.
Freedom scares the hell out authoritarians.