Depends on your definition of hard evidence I suppose but all of the anecdotal statements and decisions made by Apple would suggest they consider the Chinese market to be one of the most important for their business. In the US once you're on iPhone you basically never leave. Most US teens (85+%) use iPhone and don't plan on switching.
Meanwhile, Apple have gone on record many times underlying the importance of competing in the Chinese market and their investors ask the same questions:
Global iPhone revenue fell 10 per cent in the first quarter, but Apple CEO Tim Cook said he has a “very positive viewpoint” on China despite increased competition.
www.scmp.com
Another hint is the frequency at which Apple executives (including Tim Cook) interview with Chinese tech channels unlike their US counterparts. They really care about signaling how much they love and respect the Chinese market.
The problem with iOS ecosystem lock in as it relates to China specifically is that Chinese customers don't use Apple's services as much as we do, if at all. Most of their core 'ecosystem apps' are all domestic Chinese brands like WeChat. So moving from iPhone to Huawei in China is similar to a US Android customer going from Samsung to Pixel, there's very little friction in doing so. Meanwhile, the ecosystem apps from companies like Huawei have a much stronger pull because major Chinese brands produce so many other products that Chinese customers already use.
In China one brand can make your phone, your car, your washing machine, your smart home devices, your TV, your smart speaker, your headphones, your connected health accessories, and so on and so on. Apple don't have that in China. Look at this video for context:
Chinese iPhone sales are stagnant or dropping so there's an argument to be made that it's already too late for Apple.
The rate of progress in Chinese tech is so huge that even comparing iPhones to Chinese phones of 3 years ago is no longer relevant. By 2026 I think the difference will be even more substantial. Then the problem becomes what happens when the rest of the world (including countries with emerging economies) want to buy Chinese folding phones instead of boring iPhones. Apple's only move here is to keep up with China or risk the US and parts of the Europe becoming their only market.