Sorry, but it's bonkers to suggest ILM were designing "retro" ships to make fans think they were filming a prequel.
Huuh?!?...Who gave you that idea? I was merely speculating that the guys at ILM may have been designing models for what they
thought would be a prequel until Nimoy and Bennett told them it would be a sequel.
And the title "The Search For Spock" was ambiguous at the time. Don't take my word for it, check out the corresponding issues of Starlog, Fantastic Films, Cinefantastique