Greetings

A sourdough starter needs only flour and water, right?
We use juice in the first 3 days to provide acidity that prevents bad bacteria from invading the starter, allowing natural yeast to develop and take over from there, correct?

If so, why not use commercial yeast instead of fruit juice? We will hit the same goal. No bacteria can come near a yeasted dough. Then, as we feed it more flour, which has natural yeast and lactobacteria, plus what it would catch from the air, eventually, the yeast and the lactobacteria from the flour and the air will take over, turing it into a sourdough starter. In either cases, both the juice and the commecrail yeast will almost cease to exist in the starter.

This is probably the same reason why long preferents give bread some sour rich taste. Preparing a poolish with a tiny amount of yeast, allowing it to ferment for a day or so, would give results close to the taste of sourdough. The poolish must have caught some natural yeast from the air and from the flour.

Did anyone try to make a starter this way?
I've started my own experiment yesterday.

Day 1:
I've mixed
2T water
2T freshly milled wheat
a very tiny pinch of instant dry yeast (less than 1/8 teaspoon)
after 12 hours, I've added another 2T water and 2T freshly milled wheat

Day 2:
I've added 2T milled wheat, no water
after 3 hours, its full of holes, almost doubled and has a lovely smell (like fresh biscuits)