That’s a decent volume for each muscle group. For me, it falls somewhere between 8-12 max effort sets per week per muscle group.
When I say don’t become “volume phobic”, I meant that there’s a fine line between mainly strength gains and strength/hypertrophy. You could be getting stronger on the squat for example, but unless the rep volume is high enough, you wouldn’t make as much gains in muscle compared to strength.
The problem comes as a person gradually reduces volume each time (due to systematic fatigue) and gets to the point where they are increasing strength ok but not doing much for hypertrophy.
So it’s not exactly just a case of getting stronger (neural efficiency), it’s a case of doing enough reps per set, or doing enough low rep sets to stimulate muscle growth. You can easily get stronger doing just one or two sets of 5 reps or under on the squat every week, but it won’t do a great deal for growth.
Speaking from personal experience, I find I need to do at least a total of ~24 reps per exercise to get the best from it (assuming I’m properly rested etc)…and for me I do most body parts twice a week. So as an example, one exercise could be, 5 x 5 reps / 4 x 6 reps / 3 x 8 reps / 2 x 12 reps and so on…
Going back to the topic of cruise periods, there are many ways of doing this. One way, which is pretty good for keeping the strength up is to simply cut the reps in half so that you do not go near failure and maybe double the sets (so if doing 6 rep sets, do 3 rep sets for a couple of sessions). If you do this, you can almost guarantee that the sessions after those will be easy to go “balls to the wall”. So cycling intensity in this way is a way of guaranteeing you can continuously push to the max when needed instead of just at the mercy of “fate”.