maxspeed:practical: usage

maxspeed:practical is an “inofficial” tag which is not used very often. It seems to me that it is mainly the Russian and Dutch community where it is used.
The descriptions of its meaning which I found are rather unclear. Normally, some kind of “maximum speed” is mentioned, but also navigation.
How do you use that tag? Is following idea “correct”:
maxspeed:practical is the speed which a navigation algorithm should use to calculate the duration of a route or the expected time to destination.
Thanks for your hints.

There is description on Russian
In short:
This tag is used to map practical maximum speed achievable by typical car, for roads where this speed is lower than maximum speed allowed by local driving rules, including road signs. It is used in cases

  1. if road condition is too bad (surface and so on)
  2. if road is overloaded with traffic, pedestrians and so on

It should, yes. If navigation algorithm build path for typical car, it should use speed on this road at least as
min ( tag maxspeed:practical , tag maxspeed , default maxspeed defined by driving rules - for this road type, city limit and so on)