Opinion
This is a question that has been conjectured over for many years. There is no quintessential answer, only preferences, especially with nikasil coatings. It goes hand in hand with how to perform a break in.
Personally, after experience with a lot of race and street engine, I can say that the worst mistake to make is to overheat a new set of rings. The second worst mistake it to baby them. My opinion is that the engine should run up to temperature at a high idle and then be cooled down. Rinse and repeat a couple times. Then put it on a dyno or the track and run it hard for a short period. Cool down. Repeat. Change the oil to get the junk out, sticking with mineral based. Next change, convert to synthetic.
It's only an opinion. I have seen vehicles take 40K miles to break in on a mild break-in on synthetic from the start. Even so, they never run as hard as a proper break in because the rings never seal as well as they do with high pressures initially. Every manufacturer would recommend a slow break in because they don't care about performance, only warranty claims. A piston that isn't sealed very well will generally be denied warranty service just because it consumes oil. If its passes DEQ, good luck with a warranty complaint over oil consumption.
Many engines that are broken in at the factory when connected to massive volumes of mineral oil that is highly filtered are delivered with Mobile One. People confuse that to mean that the engines break in fine with a synthetic. Some of the newer Japanese car rings are extremely soft and seal in a different way. A starter motor can break them in. I do not know if this technology has moved to motorcycles and that is another source of confusion and misleading information. They however, will not suffer from an aggressive procedure because they are essentially already broken in after the engine starts idling. They smoke for mere seconds after start up. Honda started this in the late eighties.
Now, you can essentially find many that completely disagree with all this. I just know what has worked for me and my associates and what hasn't. You will make your own choices based upon your results but if I were you, I would flush the synthetic out, put mineral based oil in and head to the dyno or track and hope to remedy the situation without a tear down.