All the numbers say is that under the specified conditions, the film can resolve up to this amount of detail at this percentage of contrast. The maximum a film can resolve is at a very low contrast at the end of the curve. Likely P3200 using the developer stated is able to resolve what it can because at around 70 Lp/mm the perceived contrast Is still high enough likely due to the large grain size but the finer the recorded details go the grains become too large to differentiate anymore. T-Max 400 may not be as grainy but may have reduced ability to resolve more than P3200 due to its heavy use of tabular grain and dye.
Originally Posted by pentaxuser
I am not saying this is why, I am just trying to reason this out. The fact exists that this film did record this detail under the set conditions although it likely wont record that much if used normally in a real world situation.