Currrently, if we have a look at the list of bases returned by eZTemplateDesignResource::allDesignBases() we can notice that duplicates are returned :

array
  0 => string 'ezflow' (length=6)
  1 => string 'ezwebin' (length=7)
  2 => string 'base' (length=4)
  3 => string 'standard' (length=8)
  4 => string 'standard' (length=8)
  5 => string 'standard' (length=8)

This generates extra file_exists calls and this is not necessary.