Nothing odd here (perl 5.16.2 x86_64-linux, List::Util 1.35) ...

  DB<2> use List::Util 'max'

  DB<3> p max( 1 , 4 )
4
  DB<4> @p = ( 1 .. 5 )

  DB<5> @q = ( 1 .. 11 )

  DB<6> p $#p , $#q
410
  DB<7> p max( $#p , $#q )
10
  DB<8> p max( 0+$#p , $#q )
10
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