How full uptier works

It also has to do with what other players have in the queue, the MM’er can only work with what is available. That part goes with what you said about server group(s) selected, time of day and other variables too . . . . just one more thing to be considered. And even tho the “Waiting” window shows tiers, it does not reflect actual BR’s waiting, so . . very hard to say what’s in the queue exactly.

No. It will be 3.0-5.0 and 7.7-9.7

It is never more than +/-1.0 BR. Not at the same time, its + or -

yeah, if you have 4.0 tank, you can get into 3.0, 4.0 and 5.0 battles.

assorted BRs… from 1.7 all the way up to 6.0 (my max currently)

When I finally got the Sherman Jumbo I was fighting Jagdpanthers.
When I finally got the IS1 I was fighting Tiger 2s.
Seemed pointless to get a better tank since I ended up fighting even better tanks than the one I just graduated to.

Basic rule that worked for me was “Don’t use heavy tanks in a full uptier!”
Heavy tanks are the hardest tanks to play in a full uptier in my experience.
I also missed the mark with the IS2 until I learnt to do without these tanks in an uptier. Since then my stats there have been slowly improving.
I don’t know if you already know the point distribution by which you can recognise the height of the uptier.
Here are the points again:

Light Tanks Medium Tanks Heavy Tanks Tank Destroyers Anti-Air Vehicles
Uptier +1.0: 100 SP 100 SP 100 SP 90 SP 70 SP
Uptier +0.7: 110-120 SP 110-120 SP 120 SP 100 SP 80-90 SP
Uptier +0.3: 130 SP 130 SP 140 SP 110-120 SP 100 SP
No Uptier: 150 SP 150 SP 160 SP 130 SP 110 SP

And thats what I said. Each match is only 1.0 span

I think it can be a bit confusing for some when it says you can get into 3.0 battles.
You’re basically absolutely right. In my opinion, it becomes more understandable if you say …
4.0 battle +/- 0 BR
4.3 combat +/- 0.3 BR
4.7 Combat +/- 0.7 BR
5.0 Combat +/- 1.0 BR

In other words, you don’t get into a 3.0 battle yourself, but everyone else gets into your 4.0 battle.