With the possibility of many banks across Canada having discontinued ordering $10 bills, it makes me wonder if there were only a very small number of $10 bills printed for the initial run of Wilkins/Macklem signatures?
I did learn, on an article from back in 2018 or January 2019, that there were just under 20 million of the initial supply of Desmond $10s (if memory serves correctly, I think the number was either 19.6 million or 19.8 million). There were eight prefixes in the range of FTW to FFD released so far (I didn't include FFE, since the Wilkins/Poloz side, in terms of numbering, is very low), but while someone claimed in recent months that there were 70 million of the Desmond $10s released to Canada, it could be possible that that particular claim is based on the fact that there were assumed to be eight full-run prefixes, when really there may have been a lot of skipped numbers or large ranges of numbers skipped among the roughly 20 million Desmond $10s released to circulation as early as 2018.
That said, I agree that FFS and FFT are likely errors in data entry. Based on recent history, a single printing of $10 bill supply these days perhaps covers seven or eight prefixes with lots of skipped numbers. If memory serves correctly, the Macklem/Poloz $10s had only FTJ, FTK, FTL and FTM as broad runs, while FTH and FTN were changeover prefixes. This may be living proof that demand is much lower now and many banks in Canada have stopped ordering $10 bills by this point. I have never seen any Macklem/Poloz $10s in Newfoundland that was in pretty good shape as if it came freshly from a bank, implying that demand for $10s in Newfoundland is pretty much zero now. There are still $10 bills in my province, but they are the same ones juggling around in circulation for nearly a decade now.
If this latest printing of Wilkins/Macklem $10s follows the same theory as the Macklem/Poloz $10s, a realistic scenario will probably go as far as FFJ, maybe FFK. FFT is quite unrealistic at this time for a denomination whose demand is significantly lower than it was a decade ago, and it makes sense as to why there are far fewer $10s printed these days.