maybe the display, i cant tell for sure.. but this "pattern" looks right for FIR, im just not sure about the amount...
in can just tell for sure that audibly the FIR conversion seems to work fine, would the applied phaseshift be too much you would usually notice it quite easly, atleast on A/B comperasions if you have listening expierence with IIR vs FIR
it depends on your applied eq and the natural phaseshift of the speakers but for me (with some equalizer bands that tame high frequency gradually rolling off towards 25-30khz) with this eq i notice IIR vs FIR the most as in the highs seem to be tamed MORE than with FIR.. and FIR has better coherency if you imagine one bass transient and one high frequency transient played at the same time, the FIR version will sound more (or even perfectly) timecorrect, only issue is preringing with FIR... so its always a compromise
IIR because of the non existent preringing can have a more natural tone too it if you imagine a accoustic guitar recording, thats for me the most obvious hint to preringing... it can sound more "artificial" where transients seem smeared, imagine this:
instead of a instant high hat "TICK,kkk" (the first initial hit) you get something like : "ttt, TICK, kkk", tho it happens very quick (so saying "smeared transients" seem more correct)
tho having said IIR can sound more "natural" ... FIR with not too much preringing will actually sound more "real to life" imo (but yea its always a small compromise and depends on preference), thats also why inversed absolute phase is a no-go ... it will sound less correct since in nature tones are not produced with inverse polarity....
some stupid tests i did while figuring this out:
take a glass and spoon to you listening setup... try to find music that rougly plays stuff that is somewhat transient rich at the frequency of the glas when you tap it with the spoon....
now try to compare IIR vs FIR and keeping TRANSIENTREPONSE in mind and that it should sound closer to the glass transient, you will most likely notice that FIR sounds "more correct", and you might also notice how hard it actually is for speakers to produce clean, close to nature transients (it seems to go from 0 to 100 instantly where large amounts of preringing can make it seem less dynamic, more smeared etc)
things to keep in mind: dacs use reconstruction filters that ALSO either apply linear or minimum phase in various amount
if you use a two way speaker the tweeter is most probably wired out of phase... in this setup i advice to make sure that the bass driver is the right polarity and the tweeter is indeed inversed .... inverse phase is more noticable on bass drivers, it can really mess up the bass where highs merely sound a bit muted or a tad less real in comparison
also keep in mind, even with already phase shifted speakers like mine and 98% of speakers you can notice the time correct nature of FIR... just because its not perfect in the beginning doesnt mean messing it up further doesnt make it audibly worse