AGM and gel type batteries are collectively known as valve-regulated lead-acid or VRLA types. The maintenance procedures you described are for flooded batteries (FLA) and are neither required nor even possible with VRLA batteries.

You can save even more money by using FLA if you're willing to do the maintenance. If you're not, the direct comparison is with VRLA. VRLA is much cheaper than the Powerwall on an apples-to-apples basis.

It's hard to point to a specific source describing maintenance procedures that don't exist. For example, a common manufacturer's manual may be found at http://rollsbattery.com/public/docs/user_manual/Rolls_Batter.... Note the difference between FLA and AGM (VRLA) maintenance procedures. Specifically, there are none for the latter.