If Cloudflare (CF) has r/w access to the response body, which CF does have by default, then CF can easily modify or remove that <meta> tag. The risk is not abated
The risk of third parties injecting scripts, etc., e.g., analytics, advertising, etc., into response bodies (web pages) is usually cited as a rationale for using HTTPS^1
CF somehow avoids the usual objections. CF is a MiTM but few people object
1. For example, a data collection, surveillance and advertising services company that operates a www search engine and releases a web browser may not want an ISP to inject scripts, etc., e.g., analytics, ads, etc., into web pages as it might compete with the company's business. As a defense against such ISPs and other third parties that are potential competitors for data collection/surveillance/advertising services, it might favor HTTPS sites in its www search engine results, promote HTTPS at conferences discussing its web browser, etc.
The risk of third parties injecting scripts, etc., e.g., analytics, advertising, etc., into response bodies (web pages) is usually cited as a rationale for using HTTPS^1
CF somehow avoids the usual objections. CF is a MiTM but few people object
1. For example, a data collection, surveillance and advertising services company that operates a www search engine and releases a web browser may not want an ISP to inject scripts, etc., e.g., analytics, ads, etc., into web pages as it might compete with the company's business. As a defense against such ISPs and other third parties that are potential competitors for data collection/surveillance/advertising services, it might favor HTTPS sites in its www search engine results, promote HTTPS at conferences discussing its web browser, etc.