I think the TL;DR of it all is if you break it in hard, you might get a bit more performance, but potentially at a huge cost to engine life. If you break it in as per manual/easier, then you will get more average performance and a more average lifespan. Yes they break in race bikes/engines hard, but those engines also only have to last a race or two before they are rebuilt yet again.
End of the day, I'd put my faith in what the engineers said to do vs a few on the Internet. The biggest thing though, is let the engine warm up, and you don't want to rev the engine too high while cold, and you also don't want to lug the engine while riding. Varying the revs so you don't sit at a specific value (eg. 6000rpm) is also a good idea. Can easily be done by shifting up and down every few minutes, or varying speed by 10-15km/h. Some bike manuals will also say to go easy for the first 500km, then go progressively harder over the next 500 or so km.
Also, as a new rider, you need to take it slow and get used to riding. Attempting to break in a bike hard could be bad for you as well.