What you have described is not tsugi ashi, instead it is okuri ashi.
tsugi ashi : with your left foot in front, move your right foot forward first but not going past the left foot, then finally move the left foot forward.
No - i did not describe Okuri Ashi. I did not state that either foot moves in front of the other, which occurs in okuri ashi.
from aikido journal: Literally, "following steps." Refers to a sliding foot movement either forward or backward which permits smooth movements while allowing one's balance to be maintained.