So is this just another inventory whine thread disguised as a "don't put X in the cash shop" thread?

I can answer your question about retainers though, OP. With a paid for service, only about 5-10% of players will pay for extra retainers. So if there's 4,000,000 players, that means only 400,000 extra retainers (assuming that 10% buys 1 each). But if they gave everyone an extra retainers, that's 4,000,000 extra retainers... 10 times as much. So yes, their explanation makes sense.