Okay I have a somewhat different take on this and I may be way off base.

Perhaps your T was trying to reassure you that your SI scars weren't that bad as a way of normalizing or even being hopeful for you. It sounds like if you had to rip your tights to show her your thighs, she might have been worried that they were going to be very severe and was happy that they weren't. I know when I was going through all the IVF stuff my T had a hard time with any SI. His thing was that if the doctors saw evidence that I was actively engaging in that sort of behavior that they may decide that I am not stable enough to go through IVF. It may seem unfair but in a way it was true.

Sorry, my point was that perhaps when she saw the SI scars they didn't look bad enough to cause the doctors to question your stability to go through the procedures.