Most recipes for ragout call for rolling the meat in flour before adding, including one recipe whre you don't sear the meat but add it with the vegetables and everything else once the onions are done. What is the function of the flour, especially in the latter case?
Flour is a thickening agent, plain and simple. However adding it without cooking it first can lead to your dish having a raw flour taste, and you can get blobs of flour in it, so I would ignore the recipes which say coat with flour without cooking it first, or use cornstarch (cornflour) instead.
Alternatively you can make a roux with flour in a separate pan and add it in later. This is simply mixing equal weights of flour and butter and cooking it in a frying pan until it has the color you want. A lighter roux will add a paler color and a milder flavor, a darker roux adds a deeper color and richer flavor.
I don't think it's a thickening agent in this case, although it contributes a bit. Especially when you roll the meat in it, it is used for the Maillard reaction. It is a reaction between proteins and carb chains. The meat alone has lots of protein, but relatively little carbohydrates from the glucoproteins, and so it's not crisping optimally on its own.
When you add some flour to it, it crisps alone while the other vegetables are softening, it doesn't need a separate sear. Of course, you should take care to use the appropriate temperature - if it is so cold that the vegetables start stewing in their own liquid, the meat will get too wet to crisp too.
This is based on my understanding that you add the meat and all vegetables together and only later add the liquid. If you meant that you dump the liquid at the same time too, my guess is that the person who wrote down this recipe didn't realize what is happening and decided that it's easier to not wait with the liquid. Or that it is derived from a meatball recipe and the author again didn't realize that the rolling makes no sense. The thickening hypothesis is insofar shaky that there are better ways to add flour for thickening.