Looks like the recent changes to the management canister fixed those error messages. Trying to connect to asdf.com now returns the following error response:
Call failed:
Canister: xii67-oyaaa-aaaab-qadca-cai
Method: get_icp_usd_exchange (update)
"Request ID": "e94567ae5877b5e15b65553d4884c4b66bf6ffd655384612bbb3a222a5f41898"
"Error code": "IC0406"
"Reject code": "4"
"Reject message": "Connecting to asdf.com failed: Failed to directly connect: hyper_util::client::legacy::Error(Connect, ConnectError(\"tcp connect error\", Os { code: 101, kind: NetworkUnreachable, message: \"Network is unreachable\" }))"
It is likely caused by asdf.com not supporting IPv6 (as suggested by this post: HTTP POST Outcalls).
It might be helpful (and save time) to make the error message be a bit more descriptive – e.g. "Connecting to asdf.com failed: Failed to connect via IPv6.".