His name is a name that Arabs use, but linguistically, they are still aware of its Hebrew origin. It's like weak nouns in German, or how the "-ieren" suffix is attached to Latinate verbs.
Most Islamic prophets are taken from the Hebrew Bible and so have diptote names. 2aadam, 2idriis, 2ibraahiim, 2isma3iil, 2is7aaq, ya3quub, muusa, 3iisa, 2ayyuub, yuusuf, haaruun. yasuu3, the Christian version of the name for Jesus, is also diptote, obviously, as it is an Arabization of the Aramaic version of the name. Six prophet names are triptote: mu7ammad, shu3ayb, Saali7, luuT, nuu7, huud. The final three are of foreign origin, but are three letters long, and that makes them triptote regardless.
Nouns aren't diptote just for the fun of it. There are exactly nine reasons why a noun could be diptote, and when it comes to proper nouns, three categories of proper nouns are diptote: feminine ones, ones of foreign origin, and ones whose binyan is identical to a binyan that can be used for a verb.
It depends on the letters they have in their language and their culture of names. The names you might've in a language others might not have them and they then pronounce it the way they pronounce in their language
For example you don't have the name alex in arabic especially the 'x' sound so they might pronounce it as 'ك' or 'ق'.
If you need to be saying "might" so many times, maybe you're not in a position to be making claims in the first place. We'd say أليكس, not أليك (unless 'Alec' is the name we're transcribing), and definitely not أليق. And since we're talking about the same culture here, your point about different cultures handling names differently is moot: the course doesn't say Mi5aa2il for 'Mike,' but it does say 'Daoud.' Both of these are statements about this Duolingo course for Arabic right here: we're not talking about two different cultures. There is no reason to handle "David" differently. It should either say ديفيد in Arabic, or alternately "Daoud" in English.
The ending "i" is common to Semitic languages. Yitzhak Hilman in the Encyclopedia of Hebrew Language and Linguistics explains: "The gentilic suffix יִ - -ī (sometimes referred to by the Arabic term nisba) is used to form adjectives that denote some form of relation, such as affiliation, origin, or numerical order. Originally this suffix was consonantal (-iy); ... in Classical Arabic, on account of its case endings, it is still so, in fact with a geminated y that has preserved its consonantal nature. It has also been preserved in Aramaic, with a slight phonetic change, namely, יַ - -ay, especially in the plural...."