Same as I said above: you are asking for a new feature. Their default is those 20 lines that "protect" the files. If they want to offer you a way to still enable it, someone has to do it. Someone has to work on the UX of it, maybe there is a need to explain to the users why it is less secure when this feature is enabled, and then there is work to do with the criticisms that will come next time someone shoots themselves in the foot because of this feature (because "Signal shouldn't have allowed that in the first place").
I know, you will say "it's not much". But everybody asks for their "small feature", and projects generally can't do everything that everybody asks them to do (and usually for free).
I find it totally valid if they choose that they won't offer features to lower their security, and instead they will work on features having sufficiently good security. Which in this case is the secure backup.
