Maybe it's as per the design or they had difficulties in implementing it.. Not sure!
For now, we can raise or upvote existing similar feedback raised here - 40911322-support-foreach-activity-under-if-condition-and-sw
ADF Product team monitor these feedback and work on it based on no of votes, priority..
On similar note, ADF also has few more limitations like IF not allowed inside IF, Foreach not allowed inside ForEach. In such cases, most of the user implement workaround mostly using parent-child pipeline concept.
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Please don't forget to "Accept Answer" and upvote if the response helped -- Vaibhav