Well, you can detect the lib in use at compile time but that isn't necessarily what will be used at run time, things like changing the kernel or even simply setting LD_ASSUME_KERNEL differently will break it.
This is true. Unfortunately, with the current state of Linux packaging today, the assumption is that if you don't have a package available for your exact distro and version, you need to compile from source. So, for users without an RPM available, they will compile it and get this check/fix.
So I'm not convinced it's really more reliable. The real problem IMO is that we don't have NPTL rpm packages.
We do, over at newrpms.sunsite.dk iirc, the biggest problems being that I think they depend on ALSA (not sure why) and that nobody knows about them unless they visit IRC. Plus they are for Redhat only (but really it's mostly redhat users with the problems).
Perhaps it'd be easier to simply place a prominant warning on the winehq homepage with pointers to newrpms.sunsite.dk