Houston: No, I haven't heard them. I can't answer "Why" other than to repeat that it is in their embouchures (and desired tonal style).
I am not surprised that several players all may play the same mouthpiece design in seeming opposition to common wisdom (that Meyers are the hot ticket for alto) - and come up with a similar sound. If you ask me (and I know you didn't), many players sound the same, regardless of their equipment.
My favorite altoist is Paul Woltz, a traditional-jazz player who lives in Seattle. His alto is an old Conn 6M with a metal Link (at least it was the last time I played with him). While I love what he does, he sounds like a good alto, that's all (with tons of trad technique and style thrown in).
I use a Don Sinta or Meyer 6S-M on my various altos and only wish I could sound like Paul, but I'd probably never switch to a metal Link on alto (tried it already). DAVE