I do not exactly know.
To be certified, HUD must comply with a lot of characteristics. (probably "fail safe" (loss of info/sources must not confuse the pilot and must be clearly identified), readability, reliability, no risks of spatial disorientation, presences of marker, ILS LOC & GLIDE deviations, head up vs head down compatibility, display refresh rate, symbology standardization ... etc ...)
Synthetic runway is also an issue. I do not know how the synthetic runway is generated (?) If it is with the ILS LOC/GLIDE radio beam (external source), maybe it can be trusted (?).
If it is an inertial feature (like the FPM) display thanks to aircraft' inertial/GPS positioning + aircraft altitude/elevation source, it is certainly not enough reliable because it depends on a digital terrain elevation info and/or QHN setting which can be potentially erroneous.
On my a/c it is clearly not possible to land safely using only the synthetic runway as reference since positioning precision is about 10 to 20m (geo coordinates system used is xxx°xx,xx'), depends on given QNH and QNH set in the system, and also depend on runway's threshold coordinates, elevation, axis, mag variation and runway's length programmed by the crew (or present in navdata) . We must have the runway in visual.
M2000's HUD is certainly considered as: "Supplemental use" , not as "Primary instrument" ... at least, not for instrument approaches, nor for hazardous situation recovery (spatial disorientation issues).