I mean, in the same sense that it's "a problem" when a con man gives the same pitch as a trustworthy salesman.

The solution isn't for the trustworthy to stop honestly describing their products. It's to gain a reputation for honesty.

Also, you'll the know the truth from the context of your overall relationship, or, if that is thin, when they do actually reschedule.

Yes but empirically the chance of someone rescheduling is low.

So? It's not your responsibility for someone else's insecurity - and in fact, if you stop to assume that they think this way, you'll find that they 9/10 times do not.

I'm not sure how responsibility plays in. Being bluntly honest lowers your chance of making friends, in my experience.

You can't control what other people think about you. Better to just tell the truth instead of trying to shape their opinion of you.