That’s true what you say about perspective.
But look at the middle section of the contrail: it’s the same thickness all the way up (and is at the same angle to the sun).
A “false vertical” would show up as a tapering: the upper end would be thinner.
Also the lower third of the contrail shows a right-to-left smear from an low, cold off-shore or on-shore breeze (depending on the time of day). That sort of breeze demarcates sharply with altitude: it fits the narrative.
Still - I guess I should take the time to watch the video to be sure. A single still is not enough information.
Russian expert interviewed and says this was an underwater ballistic missile launch.