That wasn’t the claim. They just speculated that acquiring one solar company helped in their other solar ventures, which seems like a good default assumption.
If you have evidence that’s not the case, that would be interesting to share.
I wrote a comment 2 hours before the initial comment in this subthread that explains Tesla held in court that Solar City ended up contributing nothing because it needed to be liquidated immediately lest Tesla go bankrupt. https://www.vanityfair.com/news/2019/08/how-elon-musk-gamble...
For what it's worth, I don't even know what the inverse position would be, SolarCity was a solar panel maker, and famously, the idea after they realized they couldn't come close to China's prices, was solar roof tiles. They would be a major breakthrough project that would make Solar City a breakout financial hit.
Do people think Tesla makes solar panels? Solar roofs?
I don't blame them, I guess, this carnival has been going on for years.
I'm somewhat surprised how dedicated you are to avoiding information and asking for someone, anyone, to give info. It's been 18 hours and 3 replies on your end, albeit without people taking the time to spell it out to you like this. Personally, I would have looked into it a bit myself.