To answer your title question, meat that has been freeze dried and reconstituted is still meat. Freeze-drying doesn't remove anything but water, iirc.

However, if you are a vegetarian for health purposes, then small amounts of meat from time to time will not undermine the overall health effects of a vegetarian diet. Moreover, since fats become rancid, most freeze-dried meat will be chosen from among the less-fatty cuts, to help prolong shelf life. Lastly, as others have said, the amounts used are often quite minimal, to save expense.

If you are not religious in your observation of vegetarian diet, I'd say you can inclulde a few "meaty" freeze dried meals in your pack and still keep a clear conscience.