Why? They are no more false than "sd;kfdfs3", and "sd;kfdfs3" is just as false as them when treated as a number. Are you saying I shouldn't use something like "sd;kfdfs3" either?

$ perl -le'
    print "s:", "$ARGV[0]" ? "true" : "false";
    print "n:", 0+$ARGV[0] ? "true" : "false";
' 0.0
s:true
n:false

$ perl -le'
    print "s:", "$ARGV[0]" ? "true" : "false";
    print "n:", 0+$ARGV[0] ? "true" : "false";
' 'sd;kfdfs3'
s:true
n:false
[download]

Update: Added code.