Problems with my Upgrade...Where do I stand?

About me:
Academy grad.
Currently hold:3/M unlmtd. oceans
Mate of tow

Have been working as Mate on ship assist tugs all between 80-150 GT in the inland waters of SF bay. Since Jun 08

Currently have 425 sea days on my license.

My Upgrade

Going for a 500 T Master/Master of tow

It was my understanding that 1 year as a mate aboard these tugs would qualify me for a 500T master after passing the exam, as per CFR 11.418 Service requirements for master of ocean or near coastal steam or motor vessels of not more than 500 gross tons.

(b) The holder of a license or MMC endorsement as master or mate (pilot) of towing vessels authorizing service on oceans or near-coastal routes is eligible for an endorsement as master of ocean or near-coastal steam or motor vessels of not more than 500 gross tons after both 1 year of service as master or mate of towing vessels on oceans or near-coastal routes and completion of a limited examination.

This is the method that several of my co-workers (who are also academy grade, ie same license) used to upgrade to their 500T master.

but I thought that this would not apply to inland correct?

Would I need to adhere to CFR 11.446 Service requirements for master of Great Lakes and inland steam or motor vessels of not more than 500 gross tons ???

or could I upgrade using method (b), but for an inland endorsment?