The AC_LINE inputs have fuses on them, but the AC_TEST does not. Is this any concern?
When relay is engaged, the AC_TEST lines could have 50+A current available. The MID400 is rated for 2500V but it could fail or those 1W resisters could smoke.
The 1W flameproof resistors act as a fuse in an over-current event. They are designed to open without catching fire.