Yeah, I don't know. I'm _exceedingly_ visually/mentally sensitive to resolution being diminished by astigmatic smearing. In fact, this is my biggest problem when I get new eyeglasses prescriptions. If the astigmatism correction isn't just so, I am visually bothered by something being "not quite right", as if I can't quite nail the last 0.001% of perfect focus, and it just drives me crazy. I've learned that my eye doctor needs to check my astigmatism correction multiple times or else there is a risk that I will end up rejecting the glasses and we will have to try an alternative astigmatism correction. We both breathe a sigh of relief when I change prescriptions and this doesn't arise as an issue.
I think it is just a fact of its optical design that the FL series is intolerant of eye positioning. Some other models are as well, but many bins are extremely tolerant of off-axis viewing and eye decentering. I notice the same from some scope eyepieces (e.g. tolerant Nikon 24/30x WF or MC versus finicky 16/24/30x DS eyepieces for Fieldscopes), and other optics (e.g. my Schneider 6x aspheric full-frame loupe for 35mm versus my Rodenstock equivalent).
Note that one problem that I _don't_ struggle with is blackout/kidney-beaning. I don't seem to have much difficulty finding the correct eye distance (with any optics) to avoid such issues.
My IPD is less than average (62 mm), and though not as tight as yours, I doubt it is a factor. The FL is a stupendous binocular for those with narrow IPD as it adjusts down to 52 mm.
--AP