Chrysler starter spin down time

Hi,I replaced the starter on my 70 Dart yesterday with a rebuilt factory Chrysler gear reduction unit. it had a Denso one on it previously that finally went out so I wanted an original Mopar unit to get that old Mopar sound back. The starter works fine,but I've noticed the spin down time seems like 4-5 seconds after you let off the key. Why do these spin so long?

Edit,for accuracy I used a stopwatch and the spin down time is 4.86 seconds...is that normal for these starters?