Incremental OTA updates are great (simple and minimal downtime) provided you run pure stock (no TWRP, no Magisk).Ok. Thank you. And yes I believe I do have a copy of the C33 image. Thank you for the help. This is a lot of different than what I'm used to having come from the Nexus 6, 6P, pixel XL, and pixel 4 XL. Their method of flashing is so traditional and easy. I had gotten used to it's simplicity. Again thank you for the info.
Otherwise you have to do a bit of work to undo the modifications before you do the update. But once you've learnt how, it's fairly straightforward.
PS: have a look at my two pinned threads in this forum. They may help you to understand how things work.