Dang I must be misremembering the specifics then!

Edit: looks like fingerprints are in fact different for identical twins so it must've been that they got fingerprinted on every visit (which is much more realistic for a parole and probation office to collect and test on-site, whereas DNA would have to be sent for processing which would presumably take days or weeks)

I only heard the tale secondhand like a decade ago so not surprising that some specifics got mixed up