They say that this public or xfinity customer sharing doesn't affect speed and data used.
hotspots that Xfinity creates may not use your data allotment, but it still uses resources and overhead in your modem and router that you may want to avoid.
In Comcast-serviced apartment buildings I have seen a dozen xfinitywifi
hotspots show in the wireless connection list. Their ideology is to create free wireless hotspots across the country accessible to all Comcast customers. It used to be enabled by default, but customer blowback may have nixed that as a default.
You need to log into your Xfinity account to enable or disable (not accessible in your gateway admin login).