applying oc adm upgrade --to-multi-arch on a cluster returns either success or failure messages, where all of them are somewhat misleading:
in case of failure
error: info: Update to multi cluster architecture has already been requested
1. "error: info:" seems wrong
2. "to multi cluster architecture" sounds like we intend to provide "multiple clusters" while in fact we're intend a "multi-architecture cluster"
in case of success: 
Requested update to multi cluster architecture
3. same as 2: "multi cluster architecture" sounds misleading
in case of --to-multi-arch --to or --to-multi-arch --to-image, the error is:
error: --to-multi-arch may not be used with --to or --to-image
4. "may not be used" is ambiguous, as if it "may not be, but may be as well"

4.13.0-ec.2 but seen elsewhere

100%

1. issue oc adm upgrade --to-multi-arch command once for success message
2. issue once again for the error message
3. issue together with --to <some version> for the other error

ambiguous messages 

unambiguous messages