BitKeeper was created in large parts to fit Linux and Linus came with a lot of feedback to McVoy. Perhaps even took part in the original design? Someone who can remember can surely fill in. I never really used it, but I expect there to be some shared ideas for those reasons.
BitKeeper was distributed sccs on steroids, but kept true to its sccs heritage -- as tridge had demonstrated when he "reverse engineered" BK by telneting to the server and typing "HELP" (and following examples from it).
SCCS is a single-file revision management system, which inspired RCS (but they are not compatible IIRC; one keeps changes forward and the other backwards). CVS was a management system on top of RCS to provide "repository-wide" actions and branches. SVN was supposed to be "CVS done right".
git is a blockhain/dag content addressable storage, inspired and borrowing a lot from monotone (a system created by Graydon Hoare who later went to create rust; Linus credits monotone and graydon for inspiring the design of git, which is essentially monotone but much simplified).
McVoy and Linus did, in many ways, collaborate on making BitKeeper more comfortable for Linus and Linux development; but the design and implementation of BitKeeper predates that and goes back to SCCS through TeamWare, and maybe even farther.
SCCS uses a “weave” representation in which all revisions of a file are interleaved. Checking out any revision takes the same time; diffing is fast. RCS (and CVS) represents files as diffs backwards from the latest revision, and if there are branches, diffs forwards from each branch point.
