No, that particular message could be created by anyone (including people who are not Paul le Roux), who has the key to the 1Q2 address, at any time, past or present.
All we have to go on right now is that someone knows the private key that corresponds to the 1Q2 address and used it sometime before the last hour to generate a hash of a message that says that Paul le Roux sent bitcoin to Hal Finney.
How do we know the message was signed during the last hour and not in 2017 or 2014 or whatever? Does it include the hash of a Bitcoin block created in the last hour?
All we have to go on right now is that someone knows the private key that corresponds to the 1Q2 address and used it sometime before the last hour to generate a hash of a message that says that Paul le Roux sent bitcoin to Hal Finney.