As mentioned, "antenna vias" only have 1 connection - they could be a test point, or perhaps more likely in your case, they are indicating you have routing/net conenction problems in your PCB layout.
Thermal reliefs can be critical to good solderability/manufacturing, but the application /use of the PCB and the size of the vias must be considered. Generally direct connects are best for RF connections and for EMI containment (stapling poured regions/board edges together), or if intentionally directing heat away from pads or dealing with constrained routing spaces like BGAs. But, that doesn't mean that thermal relief vias should never be used - they are critical with larger components and large ground or VCC plane connections to ensure good solderability on the component/pad/through hole.