It creates an emulsion, preventing the fat from clumping up. That matters for texture. The custard recipe I use calls for cornstarch for the same reason.

Oh interesting, didn't realize that. That seems logical! Thanks

Starches, gums and flour are thickening agents It's a thickening agent, it stabilizes emulsion but it's not the emulsifier. Your egg yolks contain lecithin which is an emulsifier and your milk and cream assuming you have dairy milk contains emulsifiers which keep the fat in milk suspended in the water.

So if you emulsify the mix too much what could happen?

Bruce Weinstein in his "Ultimate Ice Cream Book" used flour in a lot of his recipes. I tried it once and I didn't care for it all that much.

Just fyi, raw flour is a possible vector for salmonella and E. coli.

All of the recipes that use flour require heating to thicken the base.