The Gemara uses an idiom that is found only once in Shas:

מַאן הַאי דְּלָא חָיֵישׁ לְקִמְחֵיהּ

Which literally means, who is the one who does not care to sift his flour properly. The metaphor refers to one who is not careful in his studies to make fine distinctions.

Mi Hashiloach Avos 3:17 vol I uses this metaphor to say a different peshat in the classic Mishna in Avos. The Mishna famously states:

אִם אֵין קֶמַח, אֵין תּוֹרָה. אִם אֵין תּוֹרָה, אֵין קֶמַח. 

⁦Where there is no flour, there is no Torah; where there is no Torah, there is no flour. 

The pashut peshat of the words, “When there is no flour there is no Torah” and vice versa, means that one must be realistic to ensure that basic food and shelter requirements are met in order to be able to study Torah.  At the same time, one must realize that obsessive financial pursuits to the exclusion of Torah, will eventually even lead to loss of financial security. 

However, why did the Mishna use the word flour instead of bread. Bread is the usual Hebrew idiom for generic food.  Perhaps this is why Mei HaShiloach understands “flour” or “Kemach” in the same way it is used in our Gemara.  It means sifting and sorting one’s understanding, similar to sifting fine flour.  The import is that Torah requires basic study and then discernment.  One cannot manage without the other.  Study without discernment will be lacking in understanding.  However, too much analysis without basic study will lead to a deficit in basic knowledge. Thus his way of reading the Mishna is consistent with many of the prior statements about understanding and delving into Torah.