Andreas, years ago Modern Photography magazine published an article that asked whether 100 lp/mm on film was attainable. Short answer, yes, but not consistently or easily.
I've shot USAF 1951 targets with TMX at 1:10 and 1:20 with decent LF and MF lenses. I've never got much better than 50 lp/mm, put the difference between my results and Chris' and Kerry's down to operator error. Mine. Getting the best resolution possible isn't easy. I don't doubt their results even though I haven't been able to match them so far.
I've tested two of the lenses they did, 101/4.5 Ektar and 105/3.7 Ektar. I got the same difference between the two lenses' performance that they did. The 101 is unequivocally sharper across the field.