Let me explain my point about the advantages of 4 encounters over 1 for new players in particular. Even if the end difficulty appears the same, it is not.
Say you currently have 4 encounters. I'm going to make some numbers up here for ease; they're not intended to exactly relate to any particular province or tournament
Under the current system you have 4 encounters. I am going to list negotiating costs and likely losses for each one, assuming auto fight. (The newb in question is like me and does not want to manually fight.)
1. Negotiate: 2000 gold 130 supplies 4 steel Fight: Easy peasy. Throw 5 treants at it, no losses
2. Negotiate: 6000 gold, 15 steel Fight: No matter what you do, you're going to lose a treant (or get wiped)
3. Negotiate: 1000 gold, 50 supplies, 2 steel Fight: Easy peasy. 5 treants, no losses
4. Negotiate: 3000 gold, 150 supplies, 10 steel Fight: Lose a treant, probably some archers
OK, combine this all into one encounter and you have this choice:
Negotiate: 12000 gold, 330 supplies, 31 steel OR lose 2 treants and some archers
BUT if you have 4 encounters as above, you could fight 1 and 3 and negotiate 2 and 4. So the cost to you as a new player is 9000 gold, 25 steel and 150 supplies, with no troop losses. That's a significant savings on this province.
All of these numbers are so small as to be insignificant to you bigger fellows. But they matter starting out. Especially in the beginning you want to be able to preserve those starting treants, because you can't make more of them until the end of chapter 2.
Having to make these decisions and choosing to negotiate some and fight some is also good practice for new players, who will be making this choice throughout the game (including in fighting provinces.