"smhasher discussions" where? This is not an answer.

Especially regarding "4 min" re siphash, about which kind of attack do you talk about at all, under which conditions?

The writings of those who try to protect from flooding attacks are more specific, e.g.:

https://github.com/google/highwayhash

"The author of SipHash has published C++ programs to generate" "'universal (key-independent) multicollisions' for CityHash and Murmur. Similar 'differential' attacks are likely possible for any hash function consisting only of reversible operations"

"attackers are only looking for multiple m mapping to the same bin rather than identical hash values."

"a strong hash function is not, by itself, sufficient to protect a chained hash table from flooding attacks. However, strong hash functions are important parts of two schemes for preventing denial of service. Using weak hash functions can slightly accelerate the best-case and average-case performance of a service, but at the risk of greatly reduced attack costs and worst-case performance."

Also, please also be specific about the "regressions" you mention in another post. Your statements, in the form they are, aren't of much use.