I do not currently have R81 in my lab but on R81.10 it shows Read/Write and Read-Only sessions:
mgmt_cli show sessions details-level "full" --format json
{
"uid" : "c1e96926-edf6-4578-a93b-d22dd6073fb3",
"type" : "session",
"domain" : {
"uid" : "41e821a0-3720-11e3-aa6e-0800200c9fde",
"name" : "SMC User",
"domain-type" : "domain"
},
"meta-info" : {
"lock" : "unlocked",
"validation-state" : "ok",
"last-modify-time" : {
"posix" : 1646828803274,
"iso-8601" : "2022-03-09T14:26+0200"
},
"last-modifier" : "System",
"creation-time" : {
"posix" : 1646828803274,
"iso-8601" : "2022-03-09T14:26+0200"
},
"creator" : "System"
},
"tags" : [ ],
"read-only" : false,
"comments" : "READ_ONLY_SESSION",
"color" : "black",
"icon" : "Objects/worksession",
"state" : "open",
"user-name" : "aa",
"description" : "",
"last-login-time" : {
"posix" : 1646828803271,
"iso-8601" : "2022-03-09T14:26+0200"
},
"expired-session" : false,
"application" : "SmartConsole",
"changes" : 0,
"in-work" : true,
"ip-address" : "XX.XX.XX.XX",
"locks" : 0,
"connection-mode" : "read only",
"session-timeout" : 600
}