It is common for them to refuse to give you the legally required annual credit report because the data they use to verify your identity is wrong.
Presumably, if you had your record from the dump, you could type in the wrong answers they are looking for and get your free equifax report.
Usually, only one or two of the big three have a poison record that blocks access, so I guess this would only reliably unlock equifax reports.
I believe lenders typically use a score computed by s third party - often the "FICO Score," from Fair Isaac.