Even if it was true, do you think this could be an excuse for people buying/selling bitcoins with tens of thousands?
I think it's an excuse for everyone, both small and big Bitcoin users. Bitcoin is still rather new and from my own perspective, finding banking partners that are stable and willing to work with Bitcoin related companies is maybe less than 1% of the existing banks. So we should generally be thankfully for them trying to break into a new market, knowing there can be some hiccups along the way such as this. When i initially signed up for my card, I already knew a situation like this could happen due to what I just mentioned - i think it's worth keeping in mind.
I'm not trying to say the situation is optimal or good for anyone, I'm just saying they don't appear to be scammers and they are indeed trying to sort the issues. Feel free to call it bad service from their part, I might even say the same due to their lack of details regarding what the actual issue is with their banking partners. Just don't call them a scam until they've actually scammed people. It's not like AdvCash have any interest in having these troubles, on the contrary, they are loosing money and customers over it, which i assume is the last thing any company want to happen.