The battery argument was not weak. It was actually one of the strongest arguments. Flash was a battery hog. Disabling flash on a laptop could double your battery life.
Do exactly the same animation with js or even css as you did with flash, and it will use more battery. Disabling flash turned off the animations, so obviously it saved on battery, but the reason for flash being a battery hog was how it was used, not an innate aspect of the technology.
Jobs' proposed alternative to flash, html5, did not solve the battery hogging problem, just made it move over to html5. If anything, it made it worse because you lost the quick fix of disabling flash (or rather click-to-play). That's why even iOS devices have ad blockers now, the mobile web is horrible without them.
Just try it out, especially at the time Job wrote his piece.
Of course your MBP would spin its fan and drain battery when playing a flash game. But it would do the same, and faster, when playing the same game implemented in Javascript, even more so at the time.
That's not actually evidence. I can't "just try it out", because I don't have a collection of flash games with html5 equivalents. And I still don't believe you.
Having my fans go on full blast because of Flash is something I remember happening quite often. Having my fans go on full blast because of html5 is not something I remember at all.
And your use of games here is a red herring. Nobody complained about games using up battery. The complaint was flash ads using up battery.
That's an outdated statistic. There's way too much javascript and unwanted video and other effects on the web today that your battery is still getting hammered. Turn off javascript today and you'll probably get huge battery savings.