Source on second paragraph? All the research I have seen demonstrate no measurable benefit.
While there is doubt on the hormonal responses to squats, there is no doubt that big compound lifts have a big effect on muscle hypertrophy. On the other hand, there is no doubt that the mechanism of muscle hypertrophy (including specific hypertrophy of the proteins for the type II fibers whenever that is the case) is triggered by hormonal mechanisms because, if the muscle cell upregulates its contractile protein production, then there has to be some kind of endocrinal trigger for this procedure.
It is well documented that heavy compound exercises induce the elevation of testosterone and HGH, but both of them return to normal levels within ~30 minutes. Furthermore, strength training doesn't induce elevations of resting HGH at all, and, at the moment, it is not clear whether it induces elevations in resting testosterone.
That is not to say that their impact on the hormonic mechanisms is insignificant. There is evidence to support that the most important changes for both those hormones might be on the receptor level (via up-regulation/down-regulation and changes in receptor sensitivity).
This is taken from
Strength and Power in Sports, this part is written by Kraemer & Ratamess (Kraemer also co-authored Science and Practice of Strength Training):
Perhaps more significant for long-term endocrine adaptations to resistance training is the number of androgen receptors (e.g. via up-regulation or down-regulation) potentially interacting with the biologically active free testosterone. [...] Resistance training has been shown to up-regulate androgen receptors in rats (Inoue et al. 1993). [...] Bamman et al. (2001) compared concentric and eccentric loading (8 sets of squats) and reported that androgen receptor mRNA increased 63% following the eccentric loading and 102% following the concentric loading without concomitant increases in serum testosterone concentrations. These results indicate a positive adaptation at the cellular level without significant changes in circulating hormones. It appears that muscle contractility and/or mechanical damage has a potent effect in regulating androgen receptor number, thereby increasing the likelihood of hormonal interaction and subsequent protein synthesis.
Until fairly recently, the research in endocrinological responses to strength training (and different types thereof) was focused on how each strength training program affects the serum hormone levels (acute and resting) and how those hormone levels affect strength performance. This was also the premise of study you are referring to. Now there are strong indications that the main mechanism (at least in regards to testosterone and HGH) of adaptation to strength training might not be hormone secretion but rather adaptations at the level of cell receptors.
To oversimplify, instead of producing a greater amount of serum hormones, the muscle cells might adapt to make a greater use of the existing circulating hormones.
