Texture import settings, Default is "Crunched", but I must also tick override for iOS?

I am specifying "use Crunch compression" in the default settings for a texture in its Import Settings.

However, when I switch to iOS tab, the grayed-out text doesn't mention a Crunched format for iOS.

Peeking at what Android settings tell, we see that android has indeed switched to use Crunched compression (unlike iOS)

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Should I always additionally override the settings for iOS, to ensure it will have crunched compression?

The Default tab isn't very descriptive about the format - but I just want rgb8 crunched on all of these mobile platforms.

Edit I am trying to get Crunched compression because had an impression in makes file size a lot smaller than other compression methods. But overriding iOS to use PVRTC 2 bit makes texture only 0.5MB, whereas Crunch compression keeps it at 0.7MB (lowest setting) ...Which is very weird