APP does not reject anything?

When I stack/integrate subs with APP it never rejects a single sub. No matter how many lights insert, even some with vastly lower quality than others (i.e. blurry stars) APP will simply integrate everything.
So, I did a test and used 205 subs. APP integrated all of them without rejecting a single one. Mind you, dozens of subs were really poor quality.

Then I did the stacking and integration in PixInsight (WBPP) - and PixInsight rejected 77 (!) subs.

The result of course is that the final stacked images from PI came out of much higher quality than from APP.
PI also handled the flats/darkflats much better (I have a pretty terrible spot on the camera protection glass (I hope)) and that spot was basically "erased", while APP botched it completely and dupplicated it, creating a pattern of "spots".

I have not changed any settings when integrating in APP, that is, I use the default settings and just go directly to the "Integrate" tab -- APP then runs through the whole routine of registration, calibration etc.

But I always wondered why some options, e.g in "integrate" tab are greyed out, like (I think, I cannot check right now) the option about LNC rejection or something.
Most of those are greyed out - which is why I always thought APP simply does not use that, which in turn is why from the same set of 205 subs it did not reject a single one, while PI rejected 77.

I have watched all APP tutorials etc. - but most don't actually go into detail what should one select in each tab, i.e. what about those "normalization rejection" or "lnc" or whatever parameter - in all videos I watched they just brush over them like "you don't need to change anything here just leave it as it is". Well, apparently leaving as it is is the culprit because then I have the feeling none of those functions are being used at all.