You're not listening. There are many, many reasons besides ALS and related disease for your fascics. You have presented no clinical confirmation of "wastage" or "weakness," despite seeing a neurologist who is qualified to see both if they're there.
So no, you're not presenting with flail leg or flail arm variants of ALS -- and more importantly, you're not presenting, from what you say, with any variant.
PMA is ALS with a pure LMN onset. Most likely it is/becomes ALS. It is silly to talk about LMN vs. UMN and PMA vs. ALS because there are no objective results to suggest them. I gather your neurologist isn't characterizing MND as the top candidate at this time, except to do due diligence with labs, MRI and repeat EMG -- not uncommon. So I'm baffled as to why you are, given it's a disease that no rational person would want. You've had more years of leadup to your presumed diagnosis than many people here live after diagnosis.
Please don't post again until you have more test results, as it's not productive at this point.