Ramapriya wrote

I'm sure I've come across posts from people here who seem to fly more
than one type of plane at a time, so I guess it's legal in the US to be
able to do so.
It's not allowed in my country, and was interested in knowing whether
India alone is archaic or do similar rules exist elsewhere too?

Ramapriya...there you go again...confusing these General Aviation pilots
with rules for Airline Pilots. It is true that the FAA discourages an
airline pilot from maintaining dual (or more) qualification, but it is not
against the regulations as it is in some countries. :-)

While a PIC for Air Florida (1970s), I would fly trips in both a B-707 and
a L-188 Electra on the same day. Going from a pure jet to a turbo-prop in
a matter of minutes was a little challenging. :-)

Bob Moore