Every car gets blasted at wide open throttle at the end of the assembly line on a chassis dyno which checks all vehicle functions. I’ve had throttles stick wide open on first starts, engines flew to the moon, and were some of the best running motors over the duration, just as mentioned.

i think if an engine is going to fly apart, it would be during the first few seconds, or not at all. More and more write ups say to apply max cylinder pressure as soon as possible for ring seating. A lot of the marine engine builders say on a new motor they will fire it up, set the timing, then go ring it’s neck.

I think an easy break in just makes us emotionally feel like we are doing the right thing. It is really just metal parts. Should behave the same regardless from a science perspective, and could even be best for ring seating.

On air cooled aircraft, they want you to roll the throttle on gradually as to not have the head pull away from the block due to sudden temp increasing.

Let the block, heads, and oil warm up to stable temp, then put the screws to it.

Give it a heat cycle or two. Seat the rings ASAP. Drive it like you stole it.
Our new circle track engines didn’t even get a heat cycle. We set the rings at practice, two hours before a main event.
There’s really nothing to “break in” on a new modern day roller tapper engine, other than a good ring seating session. I like the heat cycle to help head gasket seal. I always say whatever you do, don’t “lug” a new engine. Keep some rpm in it for proper oiling.
Take that thing to the track, mr. editor!