As the other poster mentioned, they're not even on the same planet as the current power density of the combined engine + fuel in an aircraft.

There are two things you are missing in these examples:

1. The motor won't scale down to a 2lbs and a few hundred watts. That's just not how it works.

2. The weight of the battery pack is partially about energy density, but it is also about the ability to discharge, which takes more batteries to make up for it. Let's say you wanted one of the motors in the article giving your device a "boost" of 500hp (sure, we can scale it back, but roll with me), your battery needs to output 400kW instantaneously. If it was a 48v pack, which is 13 cells in series, they would need to deliver 8,333 amps. Most cells are rated for something like 20a, so you need to put more in series to get the voltage high enough to get that to a reasonable number. A 400v car architecture is 112 lithium cells in series for example.

This is before packaging considerations, the increase in complexity of the base system, etc. When you look at the overall system, you're just not gaining that much. Cars are actually uniquely good for hybridization and electrification.