Sub Articulo 100.1

This is not a bug in latex. (The csname behaviour is a mis feature of
tex, but that is another story) 
On a normal sized tex installation, it is possible to have several
thousand cross references accessed via csname. This is enough for the
vast majority of documents (and for the rest you can make a bigger
tex).
If the lookup tables for cross references were implemented via token
lists rather than via csname, latex would be orders of magnitude
slower, for no apparent gain.