They used Turbo Basic in Dbase 3 & 4 as well. It was so useful that Foxpro built a migration tool to port your dbase databases and code to Foxpro. Some of the first floppies I carried with me everywhere were my Dbase databases and basic programs.

I've used dBase (DOS) III+ and IV extensively, but never saw any BASIC there. Did I miss something?

I eventually replaced dBase with Turbo Pascal plus a library named Topaz that offered most of the relevant functionality (including reading/writing DBF files).