Any seal can leak... it seems like there is evidence of it from at least a while ago - if they have good reviews, you may give them the benefit of the doubt.
It may be possible, if a pressure bleeder was used and applied too much pressure, that a seal could have ruptured or fitting split or something. I've got a motive pressure bleeder that can bleed the whole system (including master cylinder), but you're supposed to find the setting for your make/model before you start.
If you don't like what they offer, you can take the vehicle somewhere else for another opinion... tow it if you feel that strongly.
2006 Granite S