One can certainly do better and cheaper for GPS units, but for a GPS unit at a reasonable price within the PI Zero form factor, this appeared to be among the cheapest.
This is part of a stack of boards based on the PI Zero W or PI Zero 2 W. The emissions from the PI Zero, USB WIFI chip, and USB hub preclude the GPS board from making a fix. This is easily demonstrated by experiment. Having the GPS board far removed from the stack results in a rapid fix. Placing the GPS board at the top of the stack results in never getting a fix. Introducing the aluminum foil shield between the GPS board and the rest of the stack now allows fix to be achieved. Making the foil larger and slightly curved causes the GPS to achieve fix in typically seconds.
If I want to fit within the PI Zero form factor, the foil shield must be smaller and hence has less impact on the speed of achieving a fix. And for this version of the project I have to fit in app[oxiately the PI Zero W form factor. Other versions of this project typically use a GPS puck unit which does not have this problem.
Actually I can't ignore SIRF: for the application the standard equipment presently used uses the SirF chip: if I exceed SIRF chip performance then this is better than the present solution.