The test is not running on 2n-skx, but is running on:
+ 3n-skx: +8.0 +-0.4
+ 2n-clx: +8.0 +-0.5

Non-dot1q ip6base tests do not show any VPP progression, and it is unlikely the cause for ip6scale progressions applies to dot1q-ip6base, so this needs a separate investigation.