It does not make sense for PIDM to compensate your lost SGD, USD, CHF with MYR.
In a crisis, chances are MYR will depreciate sharply against those currencies, pay you 229,850 MYR now, the next moment, 229,850 may buy much less than 50k USD.
Moreover, in a crisis like a bank run, there will be a huge USD shortage in the market. Buying USD isn't as easy as you may think.
In the end, PIDM can always guarantee MYR, because BNM prints MYR. You can never guarantee a currency you don't print. The best PIDM can do is, as you say, pay you "at prevalent rates" the equivalent of your currency foreign currencies in MYR. But it begs to ask who will want MYR at that point? (Banks failing... Economy go south... 1998 Asian Financial Crisis repeats...)
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For some people, it defeats the purpose of placing USD/SGD etc. FD in the first place, should they know they get paid in MYR in the end.
But ok lah, that's just me. If you are happy with PIDM paying your foreign currency FD in MYR
in the event of a bank run/crisis, that's perfectly fine.

That is why most ppl blindly taking MCA will gives FX currencies when the fact the underlying current is still RM with PIDM protection π€¦ββοΈ
I still remember back in 98 when ppl are running around look for physical USD notes back then and as you say it is not easy to buy USD back then whether physical or through bank counters which is why the pegged was introduce to stem the outflow of RM