Question on 3 different types of cat delete pipes

[KRAM36]

I'm looking at getting some cat delete pipes. I'm really interested in the Circuit Werks pipes because they are single pipe construction and the added mounting point. I've also looked at the Top Speed pipes.

Top Speed on eBay shows that you have to buy a set per the motor in your 986. So they have a set for the 2.7 and a set for the 3.2 motor.

2.7 motor listing Porsche 986 Boxster 2 7L 00 04 Performance Catless Pipe Test Pipe Pipes in 50mm | eBay

3.2 motor listing Porsche 986 Boxster 3 2L 00 04 Performance Catless Pipe Test Pipe Pipes in 50mm | eBay

Circuit Werks listing on eBay says their cat delete pipes work for both the 2.7/3.2 motor.

Circuit Werks Porsche Boxster 986 00 04 2 7 3 2 Test Pipe Cat Delete Testpipe TP | eBay

They also have a CEL Fix set

Circuit Werks Porsche Boxster 986 Secondary Cat Bypass Delete Decat w Cel Fix | eBay

How is it that the Circuit Werks pipes work on either 2.7/3.2 motors and the Top Speed pipes don't?

Thanks for your input on this.