Why doesn't Flask streaming work on IIS?

Question

IIS

I have code:

from flask import Flask, Response
from datetime import datetime
import time

app = Flask(__name__)

@app.route('/')
def first(): return 'ok'

@app.route('/stream')
def default():
    def generate():
        for i in range(0,10):
            yield datetime.now().strftime('%H:%M:%S')
            time.sleep(1)
    return Response(generate(), mimetype='text/html') #Пробовал и mimetype='text/event-stream'

if __name__ == '__main__':
  app.run(host='0.0.0.0', debug=True, port=5001)

When running in development mode " localhost:5001/stream " I get 10 responses every second.
That is, streaming works
If I do deploy on Windows IIS, then streaming does not work (I get the whole result after 10 seconds).
It can be seen that IIS somehow blocks yield - something else needs to be configured in IIS.
How to solve streaming Flask on Windows production mode?