From S03:

$string x $count
…
The count may not be * because Perl 6 does not support infinite strings. (At least, not yet...)

However, the implementation is different:

m: say 'test' x *;
rakudo-moar ee36da: OUTPUT«WhateverCode.new␤»

m: say ('test' x *)(5)
rakudo-moar ee36da: OUTPUT«testtesttesttesttest␤»

And it seems like this behavior makes more sense. In other words, xx Inf is infinitite list, x Inf is an error, x * and xx * – currying.

Related rakudobug: https://rt.perl.org/Public/Bug/Display.html?id=125627

IRC log: http://irclog.perlgeek.de/perl6/2015-07-16#i_10908664

According to the IRC log people seem to like that.