The point is not to disable the first GPU. The point is that have the first GPU have enough extra memory for the OS overhead and still be able to load the DAG. Then the rest of the cards will run fine at 4GB. Disabling the first GPU does not solve the problem and misses the point entirely.
You know that disabling it doesn't disable it for the UI and only for the miner right? But even with one less GPU being recognised and used exclusively for the UI it doesn't work. Saying to use a GPU with extra memory misses the point that that isn't the real issue and that the miner is buggy. It doesn't recognise all memory and thinks it's out of memory when it's not. You can also see this bug when the reported memory for each card decreases each time it tries to allocate the DAG. It's also not a "solution" that always works.