You're right but the Schneeblume is not just a VF-1 reboot but part of the 2030's / 2040's Experimental Variable Fighter Program (according to Kawamori it's not part of the official series chronology for now). I mean it's not contemporary to the VF-1. This design could have been used as testbed for the VF-1 in Macross Zero but it was intended as an advanced fighter contemporary to the VF-17.
Quoted form the Macross Compendium:
"The United Nations Forces presented to every manufacturer the required specifications for SWX (Stealth Wing X), a programme to combine high stealthiness with air combat capabilities exceeding that of the VF-17. The United Nations Forces intended to assign the VF-17 the primary mission of long-range attacks, which would entail the need for a separate variable fighter for air superiority and defense.
The SV-XA1 was created as an experimental plane for these required specifications. The VF-1 Valkyrie was chosen as the basis for the SW-XA1 due to the abundance of combat data during actual warfare. This base design was improved to current standards by equipping it with upgraded engines and avionics."