While the methaphore is nice, I don't think it helps much in understanding what the point of 16GB RAM vs 8GB RAM is on iPad. So far the only use of 16GB RAM has been to avoid apps and tab reloads. Nothing else.
There is no such thing as slowdown on iPad due to having "only" 8GB RAM, only the (rare) possibility of data loss due to a reload. And to this day there is no information on any app being able to do "more" with 16GB RAM rather than 8GB.
So far the only way to keep things open for longer on iPad was having more RAM and while 8GB reloads less than 6 and much less than 4, it reloads apps and tabs nonetheless every now and then...
A 8GB MacBook will not reload at all, because it will go into swap (I have videos open since September in my 8GB MacBook and they are at the point where I left them, this would not happen on iPad).
Does swap make the computer slower? Yes, but since SSDs are very fast, especially on M series, you might not even notice the difference.
One thing many forget is that RAM usage and management in iPadOS should change thanks to Virtual memory swap coming to iPadOS 16.
Problem is we still don't know if:
- Memory swap will be implemented just like on Mac or in some other way
- how much disk will be used
- if it's at all possible to know anything about it being used or not (like you can on Mac), I doubt it...
If for instance RAM is doubled by default a 8GB device will become like a 16GB device, making the need for more RAM to avoid reloads much less of an issue. Problem is, we might never know...