[susan53]

It's true...but is, as you say, much the same as saying "although" - you're expressing concession, which means that you state /"concede") a point which seems to be leading in a certain direction but then changes tack. So :
Although he's very hard-working, I still don't think he's right for the job.
= It's true that he's very hardworking, but I still don't think he's right for the job.

So - you start by stating a positive point which leads the listener to think you're going to recommend employing the person. But then you change direction and say something quite different (and therefore, in context, surprising). That's concession.

Another example. If I say he studies 12 hours a day the logical and unsurprising conclusion would be that he's made a lot of progress. So...

Although he studies 12 hours a day, he hasn't made any progress in the last three months.
= It's true that he studies 12 hours a day, but he hasn't made any progress in the last three months.

Hope that helps??