yes there are seals between the transmission and the ptu to prevent precisely this from happening. so in essence you are running on either a mix of transmission fluid + ptu fluid or pure transmission fluid in the ptu. either way, those seals need to be replaced at minimum, which means taking the ptu off ... which then leaves you with the decision to replace/not replace the ptu while it's out.
transmission fluid is too lightweight for the ptu, certainly not fit for operational duty.
if you had regular power steering, i would have said to look at a busted pressure line as a possibility for the fluid leak, but the sho has electric steering
an explanation from ford on fluid color
drive.google.com