Yes, because the validation is called this way :
validate => 'file'
Means the rule 'file' will be loaded (both JS and PHP), we speak about the physical rule file class
This rule will instance a Javascript code with a name for handling it : file_2200
domClass => validate[custom[file_2200]]
Is calling this javascript snipplet written throught the rule class (As many snipplets are wrote as there are different validation behaviors, because it is not possible to keep the same)
ruleInstance => file_2200
Is the value sent to the rule in order to know this name. It make double use, but for the moment I must leave this. My problem is that de fields and the rules cannot call each others (Totally separated code in static, so it is difficult to play with it)
All this is not really easy. I promise you it is difficult and I do not understand why Joomla is so painfull to reallize JS front validation.
I work on that, and will fix all these annoying issues soon.
The way to make it working can change a little bit, it is not stable and not 100% clean for the moment.
When I find a better way, I will update the source.
Anyway, the PHP validation works like a charm (when regex is good of course), so the validation can be skipped for those reading here and cannot solve their problems.
Remember : to avoid the validation of a particular field, you only have to remove the class name (validate[...])
If you remove the 'validate' property, you will avoid validation both sides (JS + PHP) No validation at all.