I agree with the rest of your post but this is a stretch.
RoseQuix has documented opening 400 boosters for our convenience and despite the relatively small sample size we can assume the chance to get an agent is no more than 20% and the chance to get one of the desirable “familiar face” agents is probably 1% or lower.
Unless someone lucked out with multiple agent drops on day one, the sell 3 and buy packs for 5-10 is a long shot. The “common” mission agents quickly moved down to the 150-200k price range (and are in the 120-150k range as I type). Selling 3 of those agents in the weekend would have bought you barely 25 packs and even if you recycled everything through HexCoins, that’s not enough to guarantee 5 unique agents. Alternatively, selling an actually rare agent to gamble away with packs would be extremely inadvisable since you’re most likely to find common mission agents in the boosters.
Maybe it worked out for you or someone you know, but it was way too risky past the initial rush of the first couple days. I wouldn’t want anyone to make that gamble at this point anyway.