Did Linux have version control? That would depend on your definition of version control. It did not have a canonical version control system, but it did have the data structure for it in the form of the linux-kernel mailing list. From that a series of patches could be extracted that mirrors development quite accurately.

All subsystem maintainers had their own way of working with this. Some used svn, some used bespoke scripts.

The main reason for creating bk and git was that none of the existing version control systems matched the workflow of sending patches via a mailing list. This is quite clearly reflected in the design of git, a tool for quickly wiping and recreating a whole project directory.

Linux development history was imported to git, and you can follow it back in time since long before the introduction of git, so in that sense some form of version control can be said to have existed.