According to the above the initial question as to why the Alter Rebbe mentions that “women should recite the blessings before Torah study, for they are obligated to study [the laws governing]” the performance of mitzvot, instead of saying that they are obligated to make a blessing because the pleasure they derive from study or in appreciation that G-d gave us the Torah, can be answered.
Were it not for the explanation of the Alter Rebbe, women would be obligated to make the blessing of Torah each time they sit down to learn—and not suffice with the blessing that they make in the morning.
This is because, without a constant obligation to study Torah, there is nothing that connects the initial blessing that is made in the morning to the various times that they may study throughout the day.
It is for this reason that the Alter Rebbe explains that they do indeed have a constant obligation to study Torah. Being that they have an obligation to know all the laws of practical mitzvot, they too, constantly must study.
It is therefore understood why women too suffice with one blessing that counts for all their study throughout the day.
