The post says: "For large object structures with thousands of date time objects this can easily add up." At 0.1ms per parse, that's 100ms per thousand dates, within the range of noticeable. (Their profiler screenshot has it taking 589ms.)
Even the standard PHP string parser does 0.017ms on my 3 year old netbook.
<?php
$st = microtime(true);
$cnt = 10000;
for ($i=0; $i<$cnt; $i++)
strtotime('2014-01-09T21:48:00.921000');
echo 1000 * (microtime(true) - $st) / $cnt;
Python != PHP
Python with a jit is Pypy, http://speed.pypy.org/
Also PHP has some fast _implementations_ of PHP.
As a human, I can think a lot faster in Python. So for me, it's a faster language.