[CipherThrowaway]

The difference is absolutely not 3 seconds. That's just the lower bound.

In the case that both people are present and available in the chat at the same time, sure, it's 3 seconds. If not, that extra "hi" can add latency of hours or more. Days if schedules and availability line up badly enough.

In the delay introduced by "hi", you've created uncertainty and ambiguity for your counterpart. They have no idea whether your "hi" is the prelude to something trivial, or something important, or whether it might might be relevant to work they were about to start.

"Asking to ask" is far from the biggest communication issue in the workplace, but it is bad etiquette and a very easy behavior to correct - so why not just make the barest effort to adjust the way you communicate to better fit the medium? Save the "Hi"s and "How are you"s for synchronous communication like calls or meetings. Chat has a different set of pleasantries.