If it launches out of EA without some form of native support for a party of 6, it will be really hard not to feel that our EA feedback was basically ignored.
What it would mean is they listened to the feedback from a very small group of individuals and didn't agree with it. These threads can create an echo chamber where folks think their feedback is more popular than it actually is. Out of the million plus folks who got early access what percentage have given the feedback that they want two extra players in their party? (Answer: An incredibly small percentage)
The whole "just an echo chamber" fallacy, also known as the "just a vocal minority" defense, that a lot of people love to parrot on fan forums every single time it's convenient to their side of an argument is pointless, disingenuous bullshit, mostly for a reason: since the dawn of modern entertainment "vocal minorities" are precisely what drives the inert masses. Do you know why most of the casual audience will not even mention a 4 or 6-men party at all? Because they are not even aware it could be an option. They are blissfully unaware of what could be, in the same way they couldn't consciously tell apart any broken mechanic from a fairly balanced one. They just don't have the tools: experience, knowledge, understanding of the impact of certain design decisions, etc.
Does that mean that doing things better is a wasted effort because they will be happy anyway? No, it doesn't. Not after the initial honeymoon. Because they may be clueless, come in with zero expectations and set an incredibly low bar to be initially pleased (basically "as far as it looks polished enough"), but as they'll stick around for a while and gain familiarity with the systems they will learn to discern the faulty mechanics and their limitations. No one will need an intimate understanding of "action economy" and to read an essay on "why disengage as a bonus action is unfaithful to the original manuals" to quickly get the grasp that a combat where the most effective strategy is to constantly leapfrog around has some issues.
In the same way, there won't be any need for a long history of familiarity with the CRPG subgenre to quickly realize that carrying on an entire 80+ hours single player campaign with just the same three companions sticking around will be POISONUS for the long term variety, sense of scale, etc.
And having a day/night cycle? Pff. Most of them barely have a vague grasp on the meaning of the sentence. But they WILL start to realize that the game world seems to be frozen in a single moment in time and it will grate on them over time.
This, all putting aside that your personal claim that "a six-men party would lengthen the combat" is generally speaking a baseless stinking pile of crap, but this was a point discussed dozens of times already.