Unlike some other “posters”, I returned to the sources…And,indeed, my memoy served me right. Yichud has NOTHING to do with “lo tikrav” (the rambam quotes it as lo Tikroivu-plural). Yichuhd is prohibited (ossur) from a different posuk altogether. see gemoro Avoido Zorro 36:B.
I do not believe that the penuyos were toivel duriing Bais hamikdosh times and I think “Geshmakenstein”s assertion is, unfortunately, wrong.( the ramabam is in Hilchos Issurei Biah, chapter 22, if my memory is correct)
Someone as makpid on dikduk as yourself should not be using the word “toivel” see here