The horsepower ratings are a bit different in the last year or 2 and are less dishonest then they were previously.

Previously, charging, cooling, muffler and I can't remember the rest, were considered "accessories" and not used when testing.
I wonder how ANY of the engine makers would stand by the warranty if you removed the cooling fins off the flywheel, since they were "just an accessory"?

You may have noticed they now use "power or gross torque ratings" etc., with little mention of ACTUAL HP.
A 600 is supposedly more powerful than a 500 etc.

The earlier ratings were misleading to an extent but still useful. The old HP ratings were max output. Unfortunately, it's not safe to use a mower at 4300 RPM, and most are set to run around 3200 RPM for blade safety (max blade tip speed). So, if you had a 3.5 HP mower that was not up the job, you got a 5.0 HP. Any way you cut it, you were getting about 1.5 more HP, because all the engines were rated by the same formula. Now they are rated at max torque at the normal operating speed, which technically is a more useable value. The actual HP ratings are not even normally on the engine or in the literature. Your engine probably is rated at 6.5 lbs/ft of torque, and probably would have been rated at 6.5 HP some years ago. Whatever, you have about 1 or 1.5 more HP than a GVC 160. You will find similar ratings for other engines of similar displacement.
To just cut and bag a well-kept lawn, 3.0 to 3.5 HP was adequate for many years. Then, the HP wars started with the growing popularity of mulching, or 'recycling' and self-propelled mowers. Somewhere along the line, the issue of actual HP came up, and manufacturers eventually adapted the torque rating system to basically shut everybody up. It didn't make any difference and never did, but that's what we have.