Tesla Powerwall with 100A service?

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Oakland, CA
I've been in the queue to add a Tesla Powerwall to my existing residence with a 4KW solar panel install for about a year now. Our energy needs are pretty minor (never flipped the main 100A breaker) and the single powerwall is largely for grid backup.

Is there any reason upgrading to 200A service would be needed for a Powerwall? Their own manuals say 100-200A service is fine for the Gateway2, however the Tesla sales reps keep insisting on adding a main panel upgrade to the job and charging a premium for it. Feels like an upsell and even when I ask them to justify it with a manual or code/NEC reference from their installers/engineers they don't.

This is in Oakland, CA. I rewired entire house in the last year (with permits) to a new 200A Siemens (sub)panel. The main panel/disconnect was replaced in 2010 by an Electrician with an Eaton that's either 100A or possibly 125A (only 100A main breaker though). Main panel has been rewired now so there's only a single 100A breaker that goes to the new Siemens panel inside the house.

I prefer not to touch the service/meter or main panel because it's likely going to trigger moving the meter and main panel and/or adding concrete ballards (meter currently in a narrow driveway at front corner of house and main panel/disconnect is about 8 feet away in a recessed doghouse type enclosure facing same driveway). Plus it seems unnecessary work and expense to update to 200A service--I'm adding local energy storage to decrease my reliance on grid!

Is there some rule/reason anyone knows of for why a 200A service would be required for a Powerwall here in Oakland or California? Or is this just them trying to earn an extra premium because they can? I'm fine with adding another subpanel for non backed up loads--or moving those circuits from the 200A subpanel back to the 100A main panel (e.g. upstream of their Gateway2 device and the powerwall), which seems like generally a lot less work than replacing and relocating the meter/service/main panel.

Thanks in advance for time and advise!
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