As is often asked when this comes up on mailing-list threads about this, why does it matter what somebody uses as a terminal? It only matters what the target machine is. I can debug that target using a Linux laptop, an OSX laptop, a phone, an X Terminal (remember those?) or even a teletype, and it doesn't matter. Much debugging of production code is likely to be remote to a server in some closed data center anyway. Millions of embedded developers do the exact same thing, debugging on one platform while using another as an interface. Anyone who can't debug that way has crippled themselves. Except for those who are directly working on desktop code (e.g. the GNOME folks), good programmers are still good no matter which OS their ssh sessions are running in.

ETA: I'd be more worried about developers using brands that have been known to bundle BIOS- or firmware-level spyware with their systems, and those tend to be exactly the same brands on which people are most likely to run Linux natively. Would you rather have someone using the "wrong" platform in terms of cosmetic issues, or in terms of security?