Yep, seems thats new in R82. I get same in R81.20
[Expert@CP-FW-01:0]# clish
sCP-FW-01> set dns
mode - DNS mode
primary - Primary DNS Server
proxy - Set DNS Proxy related values
secondary - Secondary DNS Server
suffix - DNS suffix
tertiary - Tertiary DNS Server
CP-FW-01> set dns
R82:
R82> set dns timeout default
DNS timeout:
Set the amount of time (in seconds) the resolver will wait for a response from a remote name server
before retrying the query via a different name server.
The default timeout is 30 seconds.
R82> set dns timeout default