[perl #75440] [BUG] ranges from multiple application of X not working

[via RT]

# New Ticket Created by  Richard Hainsworth 
# Please include the string:  [perl #75440]
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from IRC #perl6 May 30

plain application of X works:

finanalyst: rakudo: for 1,2 X <a b> { say "$^x $^y" }
p6eval: rakudo 34542f: OUTPUT«1 a 1 b␤2 a 2 b␤»

multiple application does not:

finanalyst: rakudo: for 1,2 X (<a b> X 'x') { say "$^x $^y" }
p6eval: rakudo 34542f: ( no output )
finanalyst: moritz_: am i missing something in the second range?
moritz_: something's wrong
moritz_: I guess it has to do with list flattening