Similar situation would be with having different coins at the same seed - it would be obvious to find BTC and ETH (+ clones), but having for example Monero (or any other exotic coin) at address generated from the same seed is a different story.
Sure, but also not that difficult for an attacker to plug your seed phrase in to any multi-coin wallet and scan for hundreds of coins in a few minutes.
Instead of making it random and publishing it, why not use the username and date as a random seed, and use a pseudo-random list that you can reproduce? It's just as unlikely to be guessed, but you won't lose it.
Because now, in addition to your number pairs, you have to remember/back up the specific username and date, as well as the method/code you used to turn them in to your deterministic list. Complexity is the enemy of security, and this is all getting very complex.