Factorio Forums

In theory, you're right Heiltech.
In practice though, unless you're posting somewhere that will be seen by many people all at once, the odds of someone joining during the 30-60s someone else is joining are acceptable.
Of course, it's far preferable to be able to talk to prospective players *before* they join, but it's generally survivable without.
(Unless the game does crash, and you've got more than one impatient little shit that's spamming the join button as soon as they think the server crashed.)

I've joined a streamers game as the same time someone else joined, It works (idk how often), but its not recommended. Worst case scenario is you have to restart your game due to a crash.

I have tried pausing the game while two players joined and it didn't work. It may be due to my slow laptop.
My connection had good pings (50 and 80), and my speed is sufficient (10/10 mbps).
We got the game going and it ran smoothly after we used sequential join.