It's certainly true that "Initial Population = 0" doesn't mean "no population at all", because four of the six T1 orbital outposts have that, and yet systems created with them get a non-zero population, if a smaller one than systems created using the other options.
All of the other things without a population bar on the build have so far given much smaller population rises than the 5000ish for one of those T1 orbitals, so that seems consistent at least.
Yes. I am pretty sure that those chevrons probably aren't "1" and "2", but maybe 0.8 and 1.6.
Coriolis is 1 and gives around 15k pop. Orbis is 5 and gives 100k. Ocellus is 5 and gives 90k. Outpost is 0 and gives 9k. So what is "1"? Probably around 20k. If you have 9k on an Outpost, that'd be 0.45, or "0" rounded down.
So either a Satellite does give initial pop. Then the value is so low that FD decided to not show it.
Or it does not give initial pop. And the information in the client is correct, and it affects population in an indirect way. By giving some bonus leading to higher pop values in recalculation.
The two values "min pop increase" and "max pop increase" imho point to some base value + modification system. So "1" might be 20k in a new system, but 40k in an developed system. Because population = basevalue * modifier. So with all the <"min pop increase" is not NULL> buildings you increase the base population and with all the others you increase the modifier.
Just a theory. Imho to build a 1bn people system, some exponential pop function would be necessary. Otherwise you'd just had to stack base values on top of each other and - due to the limited amount of large stations and building slots - would necessarily end up somewhere in the 1-2 mio population range, when you have like 60 building slots.