changing version in variant

gistfile1.txt

testport1 has a variant defined like this:
variant oldversion {
    version 1.0
}

% port info --version testport1            
version: 2.0
% port info --version testport1 +oldversion
version: 1.0
% sudo port install testport1 +oldversion
Password:
--->  Fetching archive for testport1
--->  Attempting to fetch testport1-1.0_0+oldversion.darwin_22.x86_64.tbz2 from file:///opt/local/var/macports/packages/testport1
--->  Fetching distfiles for testport1
--->  Verifying checksums for testport1
--->  Extracting testport1
--->  Configuring testport1
--->  Building testport1
--->  Staging testport1 into destroot
--->  Installing testport1 @1.0_0+oldversion
--->  Activating testport1 @1.0_0+oldversion
--->  Cleaning testport1
% port outdated             
The following installed ports are outdated:
testport1                      1.0_0 < 2.0_0