John DeereNope. The MX-series cutters are "medium duty" where the Frontier are the "light duty".
Not sure where you found that MX5 listed as not being compatible with your tractor. Everything I see just shows that it requires 25 PTO HP. I don't see any specific machines listed and, even if there were, any list would be incomplete. There are just way to many machines out there for them to list them all.
Hopefully this will come through oki just noticed on the jd website that the mx5 isn't listed as compatible with the 3038e, but the frontier 5 and 6 ft cutter is. the dealership sold me a 3038e with the mx5. should i be concerned for any reason?