You said it's not lose-lose, but then gave reasons for why it is a lose-lose fight.
Saying he SHOULD get more credit is not the same as saying he will get more credit, which we all know he won't. Even you said he'd have to completely dominate 50-45 or finish a top 5 all time fighter to get any credit at all, and even that isn't true. He already did beat him when Volk had 7 months to put on size, went to Australian time zone, had 8 hours less time to rehydrate, fought at like 9 in the morning with a hostile crowd, and he still got no credit for winning because he didn't plow through him like an amateur, so it's pretty silly to pretend beating him without those disadvantages is going to convince the people who still pretend Volk was just a FW the last time they fought.
A much tougher fight that you'll gain nothing for winning is a lose-lose.
First, it seems trivially true that if Islam struggles to beat this version of Volk he should not get credit. Because this is a diminished version of Volk. But this is compatible with the fact that he should get credit for dominating this version of Volk, because this version of Volk is still a very good fighter. Given this, it it not a lose-lose situation, because there is an outcome in which Islam should get credit.
Second, the fact that some people might still not give Islam credit does not mean that he is in a lose-lose situation. Because the opinion of people who fail to track the truth of the matter is irrelevant. As you yourself noted, some people did not give Islam credit for originally beating Volk. But them failing to do so does not mean that Islam originally beating Volk was not impressive. It just means that those people are confused.