They didn't feel the need to provide multiple recommendations during the AES, or the SHA-3 process, even though Rijndael and Keccak used different constructions relative to RC6/TwoFish and SHA-2/Blake2. Why now?
So best practice would seem to be to implement both CRYSTALS-Dilithium and SPHINCS+, set CRYSTALS-Dilithium as the default, and provide a switch (config setting, whatever) to switch to SPHINCS+. If you have long-term keys, you should have both forms set up & ready to use.
SHA-3 was explicitly alternative reccomendation. The entire point was to come up with something that was not based on sha-2, because they were worried that the attacks on md5/sha1 could be extended to sha2 (which didn't really happen the way people were worried about). Even to this day, general advice is not to use sha3.
Less clear cut for aes, but at time of standardization (and even now afaik), triple des was considered secure, so its not like there wasn't a secure alternative.
These standards arent meant as implementation guides. You still need cryptography knowledge to securely use them.
Presumably, they'll have a better idea by then.
Cryptography is driven by defense applications. For all us civilian types know, these algorithms have been around for 30 years.
