This year many types of taxes have had the payment due date moved to July 15th....I cant explain the 9/15 or 10/15 payment date though.

Did you actually file on extension on or before April 15th?  If so, then Oct 15 (individual) is correct.

If not, the 'automatic' grace period provided is July 15.

All taxes are due by 3/15 or 4/15

And no, not all taxes had to be paid by 4.15.20.  Those were also provided with the grace period to 7.15.20

The taxes are actually due on 3/15 or 4/15 and extension or not that does not change. The returns are now due on 9/15 or 10/15.
That being said, there is no penalty or interest until after 7/15. Now try to explain that in the client letter.
Life is so complicated and then they add taxes to it!

tomaTOE vs  tomaTAH.....but technically I think you are right