Deja Vu

picked up strata and within the first twenty pages i was flooded with having seen this before.
you've read ringworld? same thing. artificial habitat on a cosmic scale, collapse of civilization, marooning of the motley crew - one/two rational humans, a bloodthirsty kung/kzin, search for the builders, a paranoid pierson's puppeteer and a long-suffering shand.
the two books are identical, and that's not what inspired the deja vu.

kzinti have two arms. kung have four.

i can distinctly remember, even as i read ringworld, that Speaker was supposed to have four arms. everything else fitted. i visualized him like that. so when Marco turns up now with four...

I hadn't read strata. yet somehow this one insconspicuous detail is haunting me. how can two books be so similar, and how could i see the other while reading the one, six years ago?