Different bracelet extensions on Subs

[ratty]

Hello

I have a five digit Sub and a five digit Sub date, both from about 2009.

The diver's extension on the Sub is simple to use, open clasp, give it a tug, close clasp. The Sub date's extension is different. You have to open the clasp and press one of the links to open the extension. I can't for the life of me think why they are different other than added complexity!

Can anyone tell me why the different models have different methods please?

Thanks.