Since the "load" on the tap is 50 ohms, the voltage appearing across that 50 ohm termination is going to depend on the frequency - since that determines the reactance of the series 10pF capacitor. What you've made is a high-pass filter...
When I think of a capacitive tap, I think of the typical way that an old-school RF station monitor (ham radio) was made - by using a small capacitor from the transmission line directly to the vertical deflection plates of an analog oscilloscope. Since the deflection plates "look like" a small capacitor, the result is a capacitive voltage divider, which gives a relatively constant divide ratio vs. frequency.