To add to this, custom data packs are not required. To repro you can simply disable the vanilla datapack.
Here's my game output: https://pastebin.com/Swp0ihdt
Here's the actual crash report: https://pastebin.com/ESKYnTxA
confirmed in 18w03b
Actually, upon further investigation, I think this is working as intended.
Thanks, sorry for the report!
Hmm, odd. Yes setting it to HurtTime:9s does work!