This answer https://judaism.stackexchange.com/a/93714/13680 states the following viewpoint
[...] HKB"H does not care about the truth anymore, as long as they arrived at their conclusion sincerely and wholeheartedly. Therefore it is true to say that the Halakhah is not about the truth, it is all about engaging in Torah study - that's all that matters.
Yet we almost never see poskim say "Here is one possibility" or "This is just one of many true statements that can be made". Instead it's usually something like "This appears to be the correct way", or "This is the right interpretation [of the Torah]", or even "The other Rabbi/posek is incorrect/mistaken because of xyz, clearly this is the right approach". Sometimes this latter statement is even made in strong worded language, decrying the other opinion(s).
If halachic authorities subscribed to this Eilu v'eilu view - i.e. that it's not about finding the truth, but only about the process of sincere Torah study, and that all the outcomes of this process count as true - they wouldn't express themselves as if they were seeking some actual truth or "the Torah way" that existed 'out there' independently, or that was correct to the exclusion of others. And they certainly wouldn't become impassioned about the opinions of other authorities because they perceive them to be wrong. (There is no such thing as a 'wrong' opinion in this eilu v'eilu view, as long as it was arrived at sincerely)
So do halachic authorities in practice not believe in this form of eilu veilu?