Depending on the encoding of your XML files, the -T test may or may not recognize them as "text" files. From -X:

The -T and -B switches work as follows. The first block or so of the file is examined for odd characters such as strange control codes or characters with the high bit set. If too many strange characters (>30%) are found, it's a -B file; otherwise it's a -T file. Also, any file containing a zero byte in the first block is considered a binary file.