I've never done the Judo Ashi sabaki exercises in my little bit of Judo training but since Tomiki was very high ranked in Judo I can see where the similarity would come from. Jujutsu folks I've encountered also do these sorts of exercises apparently.
To add visuals to the concept I found this vid on youtube - http://www.youtube.com/watch?v=3DF_Y6YbvnA
The first part - Unsoku Undo is the basic footwork and posture practice. The second part is an exercise in using tegatana (handblade) along with basic footwork.
Similar to Yoshinkan's Kihon Kozo, Shodokan also has a few basic drills that deal with proper footwork, postural alignment, power generation etc. I think these basic practices are a major similarity between the 2 methods.
Just my 2 cents.
Yes yes yes to the video. That was what I did when I did Shodokan. The video sure bring back memories. And by the way, Judo ashi sabaki syllabus is more limited relative to Shodokan. I remember doing lots of ashi sabaki drills during my tenure as a Shodothuglet (TM).