nyunai
In fact, the node number has never referred to transistor dimension, but the length of the gate electrode. A transistor would typically be about 4 times larger than that.
The reason to refer to the length of the gate electrode is because that was always the smallest feature printed on the chip. And that is what defined the required resolution of the lithography process.
So, a lithography process with a resolution of 32nm would be able to print chips with 32nm gate lengths.
Much has changed, and now transistors are no longer planar, they are 3-dimensional fin structures (FinFETs). The gate length scaling has slowed down, and now is not the smallest feature on the chip anymore.
The smallest feature in a modern FinFET process is actually the with of those 'fi s' that form the transistor channels.
And as if by magic, they correspond pretty well to the node names, i.e. a 5nm process will have a fin width of about 5nm.
You will likely not find that mentioned anywhere, it's just a fun fact that I noticed as a VLSI technologist.