Quite frankly, it really doesn't matter even if you make two bookings on the same airline! Even if they were on a codeshare, doubtless the name might show as a duplicate booking, allowing the airlines to overbook an extra seat!
They don't care - they've sold you two non-refundable tickets, they have your money up front, and they will have two more seats available!
With all the recent provision of all sorts of personal information being given to Custom/Immigration, it is a one-way communication, and should not normally be shared (!!!)
Regular pax travelling often on the same routing have been using tickets like that for years, and often, with careful planning, can use both coupons from the same ticket in conjunction on separate trips.
Airlines talk about service, better products, etc ,etc, but they all are in the business of making, and more particularly, laundering money! They don't care!
Per Ardua ad Astra! ........ Honi Soit Qui Mal y Pense!