Quite usual in my part of the World (EASA Land). Usually a shortcut on the STAR to the IAF and descent to the lowest altitude on the star which is the same as the IAF (12DME) crossing alt (3000’ish). The ILS “platform”altitude is 1800’ so basically from the IAF, it becomes the pilots choice when to intercept Glide Slope, 3000 or 1800. No word from ATC about it. The area is protected both upwards (from other traffic) and below (terrain).
ICAO reference? No idea.