The reason you look for proof is not that it gives you 100% security. It is the process of finding proof that helps us understand how secure a product is and what vulnerabilities need to be addressed. GHCQ's through examination of Huawei devices found problems with version control, and Huawei promised to fix those problems. This is how security could improve.

I think you also vastly underestimated how difficult it is to do version control for hardware due to extremely complex supply chain. If you examine products from any other brand, the situation is likely to be worse. I'm not suggesting Huawei's problems are acceptable. However, it is a misguided approach to decide which products are secure purely based on national origin rather technical merits.

I don't like the idea of having important infrastructure like this in the hands of any foreign manufacturer. Not while there is indeed evidence that government try to enforce backdoors in tech equipment.