A solar ready panel is a panel that has bus bars that are rated to handle more power than the main breaker because of the 120% rule. Essentially that says that the panel can be fed with a total of 120% of the bus bar rating. So on a normal 200A panel the bus bars would be rated for 200A. Applying the 120% rule means that you can feed that panel with a max of 240A. If you have a 200A main breaker that only leaves 40A left for your solar system. A large solar system will require more than a 40A breaker.
The solar ready panel will have bus bars rated at, say, 250A, so applying the 120% rule to that gives you 300A. With a 200A main breaker that allows you to have up to 100A for your solar system.
However, all that is irrelevant for a powerwall install because the solar breakers won’t be put in the meter main panel. In fact, if you have a whole house backup you won’t have any circuits in your meter main except for the feed to Tesla Energy Gateway.
The problem that you run into with a powerwall install that may necessitate the replacement of your meter main panel is that some panels don’t allow for 200A breakers on the bus. Since all of your utility power will be fed through the gateway it needs a 200A breaker in your meter main panel. If your panel doesn’t support 200A breakers then it will need to be replaced.
I don’t know anything about that panel, so it’s possible that there’s another issue with it. But just because it’s solar ready doesn’t necessarily mean that it’s ‘powerwall ready’.