The first level of the Search by Chords database (clicking “more” on the first screen) has two listings for the ♭III chord: one with 145 songs and another with 47. I checked a few tabs from each category, and it looks like ♭III chords borrowed from the minor scale go into the first category, and ♭III chords from Dorian go into the second. (I didn’t come across any ♭III chords from Phrygian.) After clicking on any other chord, they all seem to be treated the same.
Also, I found a V7/i chord from this tab in the Dorian ♭III category. I have no idea why.
These are the songs that use the phrygian ♭III. In practice
b3 is identical to
Y37 are not the same;
D3 is not identical to
b3 because the dorian ♭IIIsus4 is different from the same chord in minor.
Dorian ♭III is often a direct consequence of using ♭V in a minor key or the minor ♭VII in Lydian. When I upload analyses I always borrow from the minor mode whenever possible (e.g. ♭II in minor, i.e. ♭VII in major).
I am not at my computer right now, so I can’t see what is going on in that Theorytab. The mobile site gives both V7/i and IV/i.
Both V7/i and V7 will show up as
57/6 in the Trends database, since this major dominant seventh is itself an exception for being the only chord supermodal in the relative major that is recognized by complexity tags (and hence Magic Chord and the Trends API).
IV/i corresponds to
4/6; the correct form, IV, should correspond to the Lydian II (