I'm not a rant kind of guy, I just let my moods run away from me sometimes
I doubt you do need to do it but it's two separate things. Keeping the load and volume the same but changing sets and reps is also known as "flat loading". SE I used just to mean "submaximal effort" and I used that to differentiate going for a certain number of reps rather than an RE (repeated effort) method which would have the reps open ended and mean as many as you can do or in this case modified RE because you don't always have a specific target but you do try not to go completely to failure.
Of course we are not doing RE as Westside does but using it as an extended part of training which utilizes slow increases in volume and intensity but which also allows reductions in volume as intensity increases if need be. So that makes it more manageable over the long haul...if it works.
SE is different because you are picking a specific submaximal (like 70%) and doing it for a subscribed amount of reps and sets. So the two are very similar and overlap and basically you are using a combination of it in a way just without planning it out specifically. That means you really don't need those specific terms. I only used the term SE to differentiate something "specific" from what you are doing now.
Basically you might pick 70% of max and do a week of 4x6 then a week of 6x4 and then maybe 8x3 (maybe 3x8, etc.). It's a break from the very hard nature of the type of progression you are trying and can help get out of a rut. But if you don't need it you don't need it.