I have been a big Supporter of this theory.
However, I want to add that this MAY not optimal for long or heavily suppressive cycles. I do believe if you use 19nors that you should still use a serm on cycle. This is because, I believe, it will protect your htpa(hpga) from the damaging effects they have on it.
For me a serm on cycle is not about the having the most optimal gains. It is about protecting your htpa(hpga) from long term damage. Thus minimizing the possibility of HAVING to deal with hypogonadism and TRT.
I do believe that for short cycle a serm can, and will, minimize most of suppression.(not all by any means). Thus making PCT easier, and protecting your htpa(hpga).
Look at bloodwork with ostrine people have normalish lh and fish but tanked test levels. I believe if you used a serm on cycle you, possibly, could maintain completely normal levels of everything. Leading to NO gains lots during PCT.
With longer cycle serm may not be best for gains, as it CAN mess with other hormonal pathways that MAY reduce overall gains. Hcg could be a better option. However, this only keeps the nuts going not the the pituitary or hypothalamus.
Also ive said it a ton I REALLY question the legitimacy of any hcg you get. I won't go down that rabbit hole again though.
In the end if you goal is only gains, and you don't mind ending up on trt, then a serm on cycle is not for you.
However, if you are willing to sacrifice some gains, and to protect you htpa(hpga); as you don't want to end up on trt, then a serm on cycle is a must have.