I tried this recipe and it was a disaster. One cup of milk with only 1 TBSP of flour does not make a batter. I was skeptical but tried it anyway and my blossoms were turned into an oily mess.
I improvised for the second round and added a lot more flour, A LOT, like a half cup, and formed a real batter and had some success with that.
The original recipe must be a mistake. There is no way that that recipe works. One cup of milk plus one TBSP of flour does not produce a batter.
Do not try this recipe unless you want to ruin your squash blossoms. Ignore the recipe and make a batter that has some thickness to it.