I repeat, 'However, a frog kick meets 99% of a divers needs' and I 'seldom need to flutter'. '99%' is not '100%'. 'Seldom' is not 'never'. There are times when I will flutter. Those times are uncommon, not nonexistent. Actually, I probably use a modified flutter more often than I do a full flutter, when in situations where there are space constraints, and I cannot perform a frog kick without touching other divers, or objects. Now, as for the question, 'what kind of diving?':
First, I almost never chase underwater animals. I often find that, if I stay relatively still, I get a better view and don't startle the animals, so that they swim away. I have seen more rays - up close and personal - holding a still position on the Dixie Arrow (a WWII wreck off the NC coast) than I have anywhere else, or holding a still position on the Navy Barges on St. Thomas. I see two types of underwater photographers when I dive: those that chase animals, and those that (wisely) hold position and wait. The latter group most often gets the better pictures, and actually sees more. It is funny watching divers trying to get pictures of turtles, when they try to chase them. They usually don't get good pictures - the turtles swim away. (OK, I will even share a pet peeve here. Too often, an eager photographer who swims after the turtles to get a good picture, drives the turtle away, so others in the group don't have a chance to see the animal.) If I see a turtle swimming at a distance, I generally slow down try to gauge the general pattern of swimming, and slowly position myself for a good look. Sometimes, it doesn't work. Often it does. Squid are the same. When I see a line of squid, with the middle ones feeding while the outriggers keep watch, I slow down, and approach cautiously. They are always fun to watch. I am more interested in sea horses than I am in chasing school of fish. To find them requires slow, patient finning, and good position control (which often involves a bit of turning and back-finning).
Second, shore diving. I dive on Bonaire, a lot. Probably, it is the (or one of the) world's best shore diving location. There is often surge in the shallows along the shore line at sites on the north or south end. I may need to flutter for 5 seconds at times to get through the surge right at the edge of the water. But, as often, I get out from shore quite easily by simply timing my finning (frog kick) strokes properly, and having proper fins to allow good propulsion with the frog. If I am doing a 60 minute dive, and I flutter for 30 seconds to get through the surge, and frog kick the rest of the time, think that qualifies as using my frog kick 99% of the time.
You, and any other diver, are free to use whatever works for you. Go for it. I am not suggesting that flutter kicking is 'bad'. (Nor am I suggesting that split fins are 'bad'.) I am saying to the OP that having only a flutter kick (which is unfortunately true of many divers) is inefficient.
My advice was, and is, to the OP, who asked about finning: learn a frog kick, early in your development. Learn how to back kick, early in your development. Learn how to helicopter turn, early in your development. (These useful finning techniques are not exclusively reserved for 'technical' diving, they are valuable tools for recreational diving.) Equip yourself with the fins that will give you the ability to perform all of those kicks, efficiently. Doing so will pay dividends throughout your diving career.