Now that I think of it, I can add a few more ideas.
The formation only works towards ball possession, that's all. If you mess it up when you tank, you just lower your possession giving the opponent more scoring opportunities. Hence you lose 0-10. Simple, ok?

Now, I remember that 2 seasons ago while tanking, I encountered other tanking teams, so we both had wrong formations and some matches still ended up with me scoring 2 or 3 goals while conceding 7. How can a wrong team score this much? It should end 0-0, or maybe 1-0, except when ball possession generates his bull****s.
Maybe tactics only give a slightly higher scoring bonus for yourself. Attacking raises your scoring opportunities a little, let's say 5%, while defending it doesn't lower only yours, but the ones of your opponent up to -3%. Makes sense to me.

Let's say you possession is 70%-30%, the higher possession team gets X amount of scoring opportunities (let's say 10) that can generate goals. If you are lucky you get 5 or 6, if you are not and odds are not on your side, you get 1 or 2 and it can actually happen. BUT, on that 30% it generate less opportunities (let's say 3), that don't mean he won't score, it's just about luck and he can score 1.

The same happens when possession is 55%-45%. Both teams generate 5 scoring opportunities from which they get a final result of 2-1.

Then a troll result can happen when you are unlucky and don't get goals with the opportunities you get out of your ball possession, while it generates a goal out of lower opponents opportunities.

Just my crazy idea, but to me it makes sense, because whatever you choose won't change the result. It can be just a ratio calculated over that. Much easier to program, makse sense, mostly fair, if you lose it's bad luck.