Reliable deletion of data depends on wiping keys with hardware support. Android has per-profile keys meaning separate keys for each user and Private Space. It can reliably erase all of the data or specific profiles. It's important to reboot the device to wipe the RAM to get rid of leftover traces after wiping a profile or the whole device. Deleting a single profile may seem like a good approach but there's metadata outside the profile for it to function and it will be obvious it existed. It will be obvious it was deleted and when that happened. It isn't a system designed for secretly deleting a profile. A bunch of filesystem and OS data/metadata will be left showing it existed. Reliable deletion of the data within the profile does exist but not hiding that the profile itself existed and was deleted.

Many files will have been copied around and modified leaving traces of those around on the SSD. It's possible to ask the SSD to securely erase a span of data but it's far too late to do that after using files in regular ways for a long time. The data would often be recoverable. It would also be obvious that it happened based on lots of metadata showing those apps were clearly installed. Lack of metadata and statistics which should be there is evidence too.

It's possible to make a feature with which runs in reserved storage space where every encryption passphrase is valid and produces garbage output if the feature wasn't set up or the passphrase isn't correct. That's definitely possible. It's only realistic to make it work properly with a VM and the space for this would need to be reserved for everyone by default with the option to remove it to free it for other uses to make it properly deniable. It's still likely possible to prove it's being used via low-level analysis of the SSD.

Not possible to be forensically safe. They aren't gonna implement a plausible deniability solution that isn't robust because it will give people a false sense of security and put them in danger.