I mean it should be writable because their recommendations are that all folders in the content folder should be writable.
I had a hard time digging up the exact addition and found talk about the folder from 2021 and their automatic updating system existed for awhile. This site health check was added in 6.3 I don’t think they will change it any time soon. It is critical to the core and plugin operations.
I’d even feel iffy about adding that check here in bedrock as a MU plugin. In development environment file modification is allowed and I have and I’m sure many users do use the built in upgrade systems to install plugins to upgrade for testing momentarily, and install and test plugins.
Also since everything is managed by composer, you might even question why let the folder even exist. I"m not sure that can be suppressed as easily as automatic updates with AUTOMATIC_UPDATER_DISABLED or hiding the notice from the health checks.
I understand that the majority of users would benefit from this warning, but this is the forum for Bedrock, where in production things are locked down. AUTOMATIC_UPDATER_DISABLED is already set to true in production and so are DISALLOW_FILE_EDIT and DISALLOW_FILE_MODS which suggests to me this “critical issue” has become a Bedrock problem to solve if WordPress are keeping it here.
It also seems a bit silly that it doesn’t complain that the plugins and theme directories are not writable, but it does about the upgrade directory.
For now, I’ve just added the uploads directory with writable permissions but since this is now another place where files can be maliciously written and executed have disabled direct access from the webserver.