Yes, to the extent that workers are not hired if sv is inadequate vis a vis accumulation requirements (this shortage being the result of capital developing the productive forces as if the only limit were human needs instead of profits) and thus cannnot be a source of effective demand, their resulting poverty and restricted poverty become the proximate, not ultimate, cause of overproduction crises. If I remember correctly, note the line immediately previous to what you have quoted here where Marx argues that the employment of workers and thus their effective demand is dependent on the profitability of production. As Mattick argues, the shortage of surplus value is the ultimate cause of crisis in Marx's theory despite a few passages here and there (this being the most cited one) that only seem to contradict this argument.
yrs, rb