What does it mean that the listening callback for the 'net' module in nodejs is in setImmediate()?

Question

I have a NodeJS event loop question.

link : https://nodejs.org/en/docs/guides/event-loop-timers-and-nexttick/#why-use-process-nexttick

The link says that the listening callback is in setImmediate().

Does this mean that the callback is in the check phase queue?

When I looked at the net source code, I didn't see anything that used setImmediate. net code : https://github.com/nodejs/node/blob/61b4d60c5d/lib/net.js#L1407

Can someone elaborate on this?