Is the latter a big issue? As long as the student is not forced to repeat material that s/he already knows well, but instead can take more advanced courses or additional electives to enhance his/her curriculum at college, are the credit units of significant concern?
In terms of non-acceptance even for subject exemptions and advanced placement, it looks like those colleges that have such policies have courses and curricula that do not include courses that the AP courses are close matches for the material covered.