Minimalist Potential example not acting as expected, what'd I do wrong?

Questions
2

I deleted this since I though I understood my mistake, but now I’m confused again. It behaves as expected if you change the code to

import numpy as np
import pymc3 as pm

X = np.random.randint(0,2,10000)
Y = np.random.randint(0,2,10000)

# setup model
model = pm.Model()
with model:
    w = pm.Normal('weight', mu = 0, sd = 1)
    pm.Potential('coupling', w*(2*X-1)*(2*Y-1)/10000)

    trace = pm.sample()

pm.traceplot(trace)

The only change made is that I divided the coupling by the number of datapoints. I am confused as to why this is correct. Can someone help?