Isolating the lower portion of the abs will certainly stimulate increased blood flow to that area, which easily explains the noticeable increase in EQ. I’d say for that reason alone, working the lower abs is a worthwhile endeavor. You’re also engaging this muscle group as “thrusters” during sex, so strengthening your core in general will provide a whole slew of physical benefits.
As for the actual muscle growing and “hiding” existing penis length, I’m pretty sure it’s nothing to worry about. You’d have to work your abs against some serious weight to build that area up big enough to obscure your penis, and even then I’m not sure that it’s even anatomically possible. I’m not a fan of using added weight or resistance to my abdominal exercises. Just as with any muscle group in the body, adding more and more resistance will break down the fibers and cause them to grow back bigger to withstand the punishment. I don’t know about you, but I’m not interested in having a big, bulky, protruding waist line.
But working your lower abs will amp up the circulation down there, strengthen your hip flexors, and tone the muscle so that it looks real nice if your lean enough to see them through the skin.