No. Don’t allow for blocking.
Just be sure to lay the piece down on a smooth flat surface, being sure it is not stretched at all…and do your lengthwise measuring.
I hope you will knit a ‘gauge swatch’ before embarking on your knitting.
A gauge swatch is most important for the ‘widthwise’ stitch gauge.
If you are knitting with wool, blocking can bring the piece out to the required schematic measurements, that is, if your gauge swatch is a tad ‘off’ in stitch gauge. But it’s best to keep working with different needle sizes until your gauge is pretty much ‘spot on’.
“Row Gauge” is the lengthwise measurement. Not as critical to get exactly to the measurement required.