Mishebeirach for cholim placement
I noticed that on Shabbos, the gabbai at shul makes the mishebeirach for cholim between the 6th and 7th aliyot. I have seen this at other shuls (though I don't know if it is a codified rule or a standardized practice).
I daven at a different minyan during the week and in that minyan, the mishebeirach (which I don't always hear said during the week) is said after the Torah is read (while it is being rolled for gelilah), right before the series of yehi ratzon paragraphs.
Is there a particular source/reason that it is ready during leining on Shabbos but after leiniong on weekdays or is that (either, or both) simply a matter of convention and convenience?