Instructions for M1Rp and M1Lp are non-standard in this pattern.
Because I know how to work a M1 inc right or left, knit or purl, I didn’t read the pattern definitions for the M1p incs at first. I wondered why she was alternating the lean of the increases that were done in the same location, rather than maintaining the same lean for increases done in the same location. Turns out that the instructions for a M1Rp in this pattern actually creates a M1Lp, and vice versa.
If you follow the instructions for the abbreviations she gives, you will get the correct result, but it’s sort of like expecting someone to work an ssk every time you put k2tog in the pattern and to work a k2tog when the ssk abbreviation is used.

make m/l size

Swatched and got gauge with US size 7/4.5mm ndls

Construction is based on the Contiguous method by Susie Myers separating the shoulder “seam sts” with additional sts to create a saddle shoulder. In addition, rather than using neck shaping by casting on for only the back and shoulders and then knitting back and forth to shape the neck with increases and CO sts, all the sts are CO for the neck, and then short rows are used to knit back and forth to shape the neck. This was undoubtedly done in order to knit the neck ribbing first, rather than picking up sts for the neck later to work the ribbing.