just tested it, when you fall into shiv execute range you can use debuff remover and it'll count you as being able to get executed as a debuff. Whether or not this is intentional will be seen a future patch I guess. Weirdly enough yamatos rope, when attached, is also considered a debuff as she is approaching. Even if intentional neither abilities say they apply any type of debuff.
(Unsure if I should make a separate post regarding yamatos tether but I'm too lazy rn)