They removed Secure Delete because it doesn't work with SSDs due to the way they work at the hardware level (wear leveling).
Also IIRC secure delete is useless on APFS volumes as they are always fully encrypted, even when FileVault is not enabled.
This is what I don't get about SMS apps that may or may not send encrypted messages. (Like Apple's own)
Even at the drive level, deallocating the space used by a file is not the same as erasing it, and actually erasing every flash block that may still contain data from the file would be very expensive for SSDs to implement (both in terms of performance overhead, and in terms of burning out the flash sooner).