The 2009 data comment is in reference to the squaretrade article referenced in the preceding comment, and not to the data in this article.
I also find it interesting that no mention is made of the fact that apple updates the older devices and slows them down, to force people to want upgrades.
No, that was not what slowed down the older devices. Older failing batteries were slowed down to keep the devices running to avoid the built-in (by the batterys makers) automatic safety overdraw shut down caused by over heating.
By simply replacing the chemically depleted battery and an older Apple device would be either as fast, if not faster, than when it was new. This was amply demonstrated by millions of owners of Apple devices who did indeed replace their older depleted batteries and found that to be the case.
Apple had opted to keep the devices operational at a slower clock rate when the batteries got below their capability to provide the power demanded by the device and specific apps, rather than automatically shut down when an app pulled too much power from a depleted older battery to prevent catastrophic overheating and/or fire (something that is in the nature of lithium hydroxide batteries), leaving a user without communications in a possibly life threatening situation. The only way to reset an internal battery safety shut-down circuitry was to put the device on a charger, which might not be available.