You obviously weren't using the real elite line at the "B" gates . Actually, AA's STL "elite" line is a perfect case study in what happens when you let all elite levels through the elite line. I find that it frequently is worse than the regular line.

As to the OP though, yes the "A" side express lane is for F only, and yes that sucks for CO flyers. It actually isn't a "so-called" First Class line, it is in fact exactly what it says it is. But then again, having every flight out of STL be on a friggin' RJ sucks for CO flyers too. [Note too that of all the "A" gate residents in STL, CO is the only one that has abandoned STL completely with no mainline flights.] We all get the product CO gives us here in STL... don't get mad at the rent-a-cops!