Large difference between localhost and 127.0.0.1 on Windows?

I am testing a small webserver in python 3.8 using the Bottle framework on Windows 10 and the response times feel very sluggish.

After boiling down the example to a minimum the server looks like this:

from bottle import *
import time

@route("/now")
def time_service():
    response.content_type = 'text/plain'
    response.set_header('Cache-Control', 'max-age=10')
    return time.ctime()

if __name__ == '__main__':
    run(host='localhost', port=8080, debug=True, reloader=False)

Then a simple benchmark revealed giant response times:

def get_resource():
    with urllib.request.urlopen('http://localhost:8080/now') as response:
       html = response.read()
    return html

%timeit get_resource()
2.03 s ± 3.8 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

So this seems very odd, so I tried replacing the name lookup with a fixed ip value:

def get_resource():
    with urllib.request.urlopen('http://127.0.0.1:8080/now') as response:
       html = response.read()
    return html

%timeit get_resource()
512 µs ± 14.7 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)

Here we observe a decrease of 4000x in the response time. Where is the bottleneck here? Certainly it can't take 2 seconds to perform a name lookup on localhost?