Wow what a range of answers. Here’s mine.
Yes, I think it’s an attempt at control. What was your response? Did you say no and carry on, did you put shorts on? The fact of left you feeling odd and questioning your behaviour is a sign that should be taken notice of, well done.
I think his request was particularly unreasonable as you’re high up! Who’s going to see you?! OK, I appreciate that’s not necessarily the point but context matters. Even if you’re lying on a glass floor, which presumably you’re not, you still had knickers on, who is looking up? And so what if they are, you’re not harming anyone. Exactly, no worse than a bikini. I think it was about his overall issues with how you conduct yourself rather than that particular context.
As for his comments about your social media activity, he sounds very judgemental, how well does he know you? Are you posting with a pout in a seductive manner? It doesn’t sound like it.
If he’s meant to know you well, and he still looks at what you’re doing with a misogynistic slant, (is that the right word here?), then that’s also concerning. Surely he should know that your motives are genuine and innocent? Obviously, this also depends on his tone of how he said it etc..
He’s entitled to his more conservative opinions, just make sure they don’t control you and your behaviour, and erode your sense of self.
I think I would be reviewing previous behaviour in case I’ve overlooked anything else telling, and also his overall contribution to my life, but we are all different in some ways, you just have to be aware of what you’re willing to accept and tolerate in this particular relationship combination. What is he like with communication? Can you discuss this like an adult with him, or does his ego get in the way? That also might tell you a lot.