Clearly, the water may be in direct contact with the 220 or 230V phase line voltage inside the shower head.
But normal tap water has a high resistance, and this resistor (of the water touching the body) is in series with a user's body resistance. It is not (directly) the voltage that is dangerous, but the resulting current that may flow through the human body. The danger starts at ca. 10-30mA. So the total resistor (body + water) must be greater than ca. 20000 Ohm. Tap water has a higher resistance even for the short distance between the wire contact zone and the shower outlet, whereas a human body's resistance (salt, ions, water) may be as low as 500-5000 Ohm @ 230V, but is in series with the high water resistance.
Furthermore, the water with the 3 power contacts in the head forms a voltage divider that does not feed the full 230V into the part of the water that leaves the shower head.
Answers to the comments:
In the first picture, there is no insulating to be seen between conducting metall and the water. The junctions are soldered and/or crimped without any insulating coating. The coiled heating wire itself is neither insulated from the surrounding water.
A simple 50 or 60Hz transformator that would insulate the shower head circuit from the main circuits is much too expensive, heavy and bulky to be part of these simple showers, given the needed power is in the kW range.
Heating elements for conventional kettles, washing machines, dish washers, water boilers etc. are almost always of a type with full insulation between the metal parts connected to 230V and the water. Only in recent years there are types of electronic tank less water heater or flow through heaters where the conducting heat element is in direct contact with the water in order to improve speed and efficiency and to avoid lime stone coatings (thin wire expanding and contracting by heating/cooling down).
There is no galvanic insulation, there is no hollow wire, the terminals are not insulated by a hollow construction. The full mains voltage is in contact with the water.
The green yellow earth wire provides protection against cases when the conductivity of the tap water is too high (= resistance too low) to be harmless. The mandatory standard 30mA RCD switch trips the mains if the difference between phase and neutral becomes greater then 30mA, what could happen in case of contamination of the tap water with detergents, sewage water, sea water, or minerals/residues after work on the water net etc. Since this wire is much closer to the wire parts with high voltage then the user's body, it will trip before dangerous currents may flow through the user.