Per : we added structure so that the time separator could depend on the number system being used for time digits, and added data so that in locale "ar", for number system "arab", the timeSeparator value is '،' (U+060C ARABIC COMMA). This appeared in CLDR 26 / ICU 54.
We have gotten feedback on this from our Arabic testers and users: "comma was used in old text books, but never in electronic format." In computer & mobile device usage, the expected formats use colon.
I suggest leaving the structure in place but changing the ar/arab timeSeparator value to ':' COLON.