Battery questions on 2019 RAV4 Hybrid

Just so I'm clear on this - I'm reading that the 12V battery does NOT start the the car. They hybrid battery does that. BUT - the 12V needs to be working so the hybrid battery can do its thing? Is that right? Didn't have much luck finding good info on that. Got home from a 10 day vacation and the battery was completely dead. Charged the 12V up via the terminals under the hood (took about seven hours) and it finally started. The hybrid battery full minus one bar (same as before I left).

One other thing - I saw another post on here awhile back about not needing a $1400 12V battery, which the dealer might try to tell me. It seems that a regular TrueStart 00544-H4052-470 for around $200 is the exact same thing, and that I can just change that myself. Any thoughts on this? Thanks so much gang!