Nevertheless there are surge protection standards for instruments (e.g. in said IEC 1000-4-5) which deal with the surges bypassing the first protection levels.
Which means we are discussing a transient that exists before it is even on wires that provide electricity to a building. Obviously IEC1000-4-5 is only about an item. It is only a tiny part of a bigger picture.
To protect any appliance from a surge that can easily blow through that 4000 volt protection means addressing that surge where it is most easily eliminated before it can enter a building. That solution is typically located at a service entrance and always with a low impedance (ie less than 3 meter) connection to single point earth ground. Only then is protection defined by IEC1000-4-5 not overwhelmed.
Does not matter if every other ground connects to that earth ground. Those are irrelevant. Impedance of that connection must be low. That connection must have no sharp bends. It cannot be inside metallic conduit. It is separated as much as possible from other non-grounding wires. It must have no splices. It must have no sharp bends. It must be low impedance.
A protector is only as effective as its earth ground - electrodes in earth. Should damage happen, an investigation starts by locating a human mistake that made damage possible. That starts at the item that must always exist to have effective protection - single point earth ground and connections to it.
Best protection on a TV cable is a hardwire direct to that earth ground. A protector only does what a direct hardwire does better. Effective protectors are only connecting devices to what defines protection. To what harmlessly dissipates hundreds of thousands of joules. That is an always required single point earth ground.
Classic example of HDMI port failure is a surge incoming on AC main. And outgoing to earth via some other path. HDMI port is a classic outgoing and destructive path to earth via its cable or satellite dish connection. That connection path can include any signal wire, analog, instrument, or digital ground inside electronics, and any 4000 volt protector. It is the nature of a classically destructive surge; that is a current source.
Protection is always about where hundreds of thousands of joules are harmlessly absorbed. A protector is only as effective as the quality of and connection to its earth ground.
Concepts that define protection of appliances inside a building were demonstrated by protection of that building - when using a lightning rod. In every case, protection is defined by what harmlessly absorbs even hundreds of thousands of joules. Best protection for HDMI ports exists where that surge might enter a building. A solution that typically costs about $1 per protected appliance.
BTW, protective ground is about a resistance connection. For surge protection, impedance (not resistance) is the critical parameter. So we discuss earth ground - a subset of what is described as protective ground. A low impedance connection is always possible. Why were we always able to achieve one? It is required for effective protection even of the HDMI port.