If the antenna doesn't perform adequately one would know pretty quickly. It simply wouldn't be able to pinpoint location accurately.

Plus, that antenna was just an example. Clearnav sells a similar one for about $40. I'm busy fitting an antenna sharing box for my clearnavs and Flarm so I'll have a couple spare. And I've never heard of anyone finding those unsatisfactory, other than occasional location related problems.

Ignoring quality differences, are there technical or FAR related reasons not to do this?