Thank you greatly for the detailed explanations! We are aware of both "designated marksman" (and yes, the SVD is not a sniper rifle, this is a typical "Marksman", which, however, snipers use with success) and about the difference in tactics between Marksman and Sniper, and about the ability to fire from a sniper rifle at close range. We have studied the issue in detail, we have consultants.
However, the game doesn't claim to be 100% realism in life and introduces its own conventions so that the gameplay is interesting and understandable for the majority of players, and not only for 1% of those who really
a) seriously understand the issue
b) require at the same time from the game of such realism
The close range penalty is necessary for sniper rifles (let's call anything that is both sniper rifles and Marksman weapons) to balance with other weapons/skills in the game, and not for the sake of maintaining realism. Nevertheless, it can be justified logically (indeed, in reality, hitting moving targets at close range from such weapons is much less convenient than from an assault rifle, for example; it should be remembered that the game is turn-based, i.e. if the character is standing still - this doesn't mean that he doesn't move "conditionally". It means that it's simply not his move, this is another game convention that strikes such nuances).
As for the terminology, the absolute majority of players will not understand the term "Designated marksman" or Marksman, while "Sniper" is understandable and transparent. You see, these are the stereotypes that have developed as a result of movies and games, which are at odds with real military terminology and tactics. It's possible, according to the same logic, and about shooting with a "silencer" to expand the topic, what are silencers in general, and why we call an ordinary "can" a silencer :) These are game conventions and generally understood stereotypes.
Thank you for your understanding! We hope that such conventions won't prevent you from enjoying the game! Just note that we did it on purpose, not out of ignorance. :)