interleave and strings

Consider a patter as below:

<interleave><anyString/><string>true</string></interleave>

In my understanding, this matches "true", "0t0r0u0e", "1111t8rtu2342e".

Another example:

<interleave><data type="xsd:integer"/><string>13</string></interleave>

This matches "1234", since it is an interleaving of "24" and "13", where 
"24" is an integer.

I think that this makes implementation very difficult or even impossible.  
Furthermore, I see no values in allowing such patterns.

Cheers,

Makoto