Their security teams are industry-leading and they have done a lot of important work over the past decade (Project Zero, a very well-done bug bounty program, Advanced Protection, FIDO/hardware security keys, large-scale fuzzing and AFL, tons of behind the scenes sandboxing work, Linux kernel hardening...). They have a fine track record keeping their users safe (...from anyone but themselves and the US government).
> Given the embedded browser is not secure
It's a standard web view, which uses the same engine and is sandboxed the same way the standalone Chrome browser is. There's a few extra APIs injected into it, but chances are that they require authentication or simply check the origin. What makes you think they didn't take this into account when triaging the report?
There's hundreds of these web views with plenty of opportunities to "escape".
> Now, Google only fixes security bugs only after they've combined into a severe remote exploit
[citation needed]
Things like Chrome entirely rely on multiple layers of protection and, like any sensible vendor, they will absolutely fix a bug in, say, the renderer process even if there's no full-chain exploit.
> In some contexts (especially as high-stakes test settings, but also some military/prison/finance/medical/legal/etc. settings) this IS a direct security risk
In a kiosk or proctoring environment, you wouldn't be able to browse Google account settings in the first place. It's a non-issue.