We had a few months ago, exactly this query. The way the "homes" work is each axis moves singly, and, yes, Mach is only looking for a signal from that axis, It then does the other axis. The problems then start, becasue if one of the switches is tripped out of sequence, the switches act like limits and stop all movement.
I did not follow the post to it's conclusion, but seem to think that there is a way to "slave" both axis together and have the "home" acting together. Another search is called for, unless the "poster" points the way to it.