Yes, thats right. I have thougtht about this solution,too. There is one reason, why I include both css files: the .css files are included in the header. There would be one additional SQL request on each page, only to check which lightbox have been chosen- not really smart.
There must be a better solution..
May be its better not to integrate a lightbox.
If you want to “solve” the problem, you can simply delete the .css file.