That stripe is painted correctly if spoiler was dealer installed. According to the CRG, there are many documented examples of cars like this.
From the CRG web page:
Q: What is the correct trunk lid striping for a Z-28 with a spoiler?
A: If the spoiler was installed at the factory:
- The paint stripes go over the spoiler, and end at the bottom of the spoiler (and therefore not on the back lip of the trunk lid)
- The Camaro trunk lid emblem was moved forward, up the trunk lid, from station 125.00 to station 121.73, a distance of 3.27 inches, and the Z stripe was masked (1967-68 only) around the emblem.
If the spoiler was installed by the dealer:
- The stripes were painted on the trunk lid at the factory and thus, without a spoiler, run all the way through to the lip of the lid. The dealer installed spoiler was attached over the factory stripes and then the dealer painted the spoiler to match.
- The dealer did not relocate the Camaro emblem.