Checkout - Password Doesnt Match When Not Creating Account

When checking out, I used by browser autofill which also added something in the password field. I clicked that I do not want to create an account which hid the password fields. Then when I clicked next I got a "passwords do not match" error, which is confusing as the password field is not shown. I had to uncheck that I do not want an account, remove the data from the password field, and then check the option again before proceeding. I realise that this may be rare as I have probably used many emails and passwords when testing the site over the years and autofill has just done its thing. Even so shouldn't the contents of the password field be ignored if not creating an account?

It is probably populating your saved admin password. 

I've made a note of it.