Why do exes block you on one thing and not anything else?

This has always been funny to me. Me and my friend were talking and she told me her ex out of nowhere blocked her on Instagram but kept WhatsApp open. During their relationship she said when they’d get into fights he’d block her on everything so it isn’t a matter of forgetting.

Is this manipulation that some people use to get you to contact them?
Why do exes block you on one thing and not anything else?
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