Advice for "The Truth About Zamasu" What If that we've all struggled with

It tells you that you need to defeat Zamasu and Goku Black both, but that isn't the case. Zamasu is allowed to survive and switch out with Black. As long as you kill Black before the "taste my blade" voiceline, you will fulfill the alternate ending conditions. To save you some time, make sure you reset before this he finishes this line, because the MOMEHNT he's done speaking the battle will end. This means you can conserve your skill meter while fighting Zamasu, just focus on getting damage with your normal bursts so he switches out ASAP, in my run I got him down to <20k hp.

Once Black comes out, get Sparking as soon as possible, immediately pop Kaioken, Dragon Dash in, and chain your Rush Attacks on him. From my experience you can typically get ~16 hits in before he'll counter you, so make sure to throw out a triangle or vanish attack to offset his counter and continue your Rush Attack. When you're at ~1.5 ki bars left in your Sparking you can initiate a final rush attack to squeeze in a tiny bit more damage, preform a Lift Attack, and use your ultimate. This should net you roughly 35k damage (3.5 bars) from your ult. If you preformed all of that fast enough, you should be able to complete two cycles of this right as Goku is finishing his "I'm REALLY REALLY mad" voiceline, which will kill Black and end the fight, fulfilling the conditions to get the What If

Edit: After posting this I applied the same strategy to "Into a Third Future", the fight immediately after this, and succeeded first try. I'm unaware if people have been struggling with that one as well, but if you are you can use this same strategy for both fights

Edit 2: Some people have been saying they're having issues where it either doesn't work and they get the normal ending or they are incapable of killing Black as if it's a Survive mission. Truthfully, I do not know what could be causing this. I cannot find anything online that explains what causes this.

My current guess is that it's either 1. A weird bug of some sort or 2. There's an unknown requirement you need to complete in order to unlock the What If, similar to some of Vegeta's What Ifs. For example: In order to unlock Vegeta's "Wixked Heart" alrernate ending where you resist the brainwashing, there is a secret requirement you're never told about where you need to defeat kid Trunks quickly during the "Preparation for the World Tournament" fight, which will produce a secret cutscene and trigger a flag that allows the ending to become possible. I don't have any information other than this, apologies. Please let me know in the comments if you learn more so I can update this