ah, there is. talk to Honda engineers. here are the rules for a 500 to 1000 mile breakpin:
1. do not drive at constant speeds for very long; vary by 2-300 rpm over say 15 minutes
2.gradually increase maximum rpm in 500 rpm in increments from 3000 to 7000 rpm; don't keep it at max rpm more than a few seconds
do not drive for short trips under 10 miles.
4. do not slam throttles wide open unless you have to. do not pound an engine within 5 minutes of starting unless absolutely needed for safety.
5. do use a injector cleaner every 500 miles tat doesn't have alcohol as an ingredient.
6. keep an eye on valve clearances. not critical but could be.
7. don't change oil until at least 1000 miles and by 1500 miles. use good synthetic oil. always change filters with oil changes.
all mechanical parts have a wear in period; its just the nature of them. nothing doesn't wear with time and service.

Does this exist anywhere in writing??

The posts above are a total BS.

Could not find anything in my manual for my 15 EX Fit.

good advice.

Modern engines require less "break-in". Why? Because the parts are machined to much higher tolerances than what they were years back. Break in is a matter of letting the "rough edges" wear in and seat so that the parts are smoother and fit better.
Some will tell you to beat it from zero miles. You might and get by with it if you are lucky and everything fits just perfect. But doing a fair break in is always the safest route to take. On new cars today its not difficult, just avoid those full throttle runs and high RPM for a few hundred miles.

Oh, so you know, I am not one of those "racing experts" or anything. I just spent many decades in the industry as a technical person inside the pieces and parts and working with the design and manufacturing engineers. I have seen the insides of more engines, transmissions and other parts than I care to remember. Never saw a vehicle that was damages by a careful break-in procedure. I have seen some that were hurt by trashing them too soon. If you have a tight cylinder you can get a hot-spot and score a ring or a cylinder wall.

I have seen engines that after over 100,000 miles were torn down and still very much within factory specs. You are more likely to have worn seals or bad gaskets from age and not changing oil than to wear out other moving parts. As I use to ask the students, "How many parts are rubbing against each other in a running engine? NONE! That is why we have oil.

Taking care of a vehicle pays off down the road. Break it in right, keep good oil in it and it will give years of service.

600 miles is the safest !

This is from the manual for my 2016 Fit LX.

"During the first 600 miles (1,000 km) of operation,
avoid sudden acceleration or full throttle operation so
as to not damage the engine or powertrain.
Avoid hard braking for the first 200 miles (300 km).
You should also follow this when the brake pads are
replaced."

That's it. Direct from the factory

In other words, don't do to the car what you (or others) did to it during the test drive? :D

1500 miles change the oil drop the hammer

I look at it this way.
I'm not even going to really worry about or enter the debate about whether you should or need to break in the engine.

If Honda recommends taking it easy for 600 miles?
Even if you disagree, that's barely 2 tankfuls of gas.
I think I can afford to wait that long, or give the vehicle that much "respect" whether it's helpful or a total waste of time.