When selecting multiple items the order in which they’re selected should be reflected in how they’re processed.
When I select three songs and then hit “play” the first song I selected should play first, and the rest in the order I selected. As implemented they play in “lexical” order (i.e. the order in which they appear in the list from which I selected them).
The only use-case I have for multiselect is to create a listening queue, and un-ordered selection breaks that. As is I have to long-press the first track, hit play, long-press the second track, hit “add to queue”, etc.
I would argue that not respecting order breaks the principle of least surprise. Other Android multi-select implementations respect order (e.g. adding photos to a social media post or SMS message).