I don’t know the version of the dng specification used by these older iPhones, but they are correctly processed by Photolab.
It is equally important to understand that Photolab relies on a builtin list of supported phones and their raw formats.
The models supported are baked in the photolab application. For example, PL can process iPhone 8 Plus dng files, but not those from Samsung Galaxy series. With an easy manipulation, you can fool photolab into decoding some dng files produced by Samsung phones.
See this : While waiting for a smartphone/dng solution from DXO PL - #5 by Joachim