Jonah,
Fair question and I suspect someone from ATP Admin may chime in. Until then I had this conversation with a friend of mine who’s a DPE (he’s actually one of the DPE’s ATP uses). While the inspector you met at your local FSDO may be ready and willing to give you a checkride, the vast majority are not (hence the very reason the FAA created the DPE position). FAA inspectors wear a variety of hats and have many responsibilities and apparently taking a half a day to do a checkride is not an efficient use of FAA resources since the FAA Inspector shortage is worse than the DPE (just check the USA Jobs website, you’ll see HUNDREDS of openings). From what I understand scheduling a checkride with the FAA would further delay the time frame. On a side note I do agree the FAA (aka Feds) get a bad rap as most I have met are quite pleasant and helpful. They are some of the best airmen alive and I would NEVER EVER say anything disparaging about these EXTRAORDINARILY fine group of people (so please leave me alone!).
Adam