Question about Poisoned Roots, part of the dark gift Mist Walker

From Ravenloft: The Horrors Within... 

Poisoned Roots. When you finish a Long Rest, the world around you in a 10-mile radius becomes a siphon that leeches away at your vitality. Whenever you finish a Short Rest in that area, make a Constitution saving throw (DC 13 plus your Proficiency Bonus). On a failed save, you get no benefits from finishing that rest.

The save for Poisoned Roots is DC13 CON plus your Proficiency Bonus. For my 5th level character that makes it a DC16 save. It also means that when my character is level 9 and then has a Proficiency Bonus of +4, the save DC is DC17. As my character progresses the save gets more difficult.

My character sheet on dndbeyond.com confirms this calculation.

Is this how it's intended to work? If so, can someone help me understand why it works this way?

Thanks in advance.

Quote from conklin94122 >>

From Ravenloft: The Horrors Within... 

Poisoned Roots. When you finish a Long Rest, the world around you in a 10-mile radius becomes a siphon that leeches away at your vitality. Whenever you finish a Short Rest in that area, make a Constitution saving throw (DC 13 plus your Proficiency Bonus). On a failed save, you get no benefits from finishing that rest.

The save for Poisoned Roots is DC13 CON plus your Proficiency Bonus. For my 5th level character that makes it a DC16 save. It also means that when my character is level 9 and then has a Proficiency Bonus of +4, the save DC is DC17. As my character progresses the save gets more difficult.

My character sheet on dndbeyond.com confirms this calculation.

Is this how it's intended to work? If so, can someone help me understand why it works this way?

Thanks in advance.

 What it does is cancel out your proficiency bonus if you are proficient in the save, so the save stays the same difficulty unless your constitution changes.  ie, if you have a 16 Con, it will always require a roll of 10+.

If you're not proficient, well, ouch.

Yes, that appears intentional.

Quote from conklin94122 >>

Is this how it's intended to work? If so, can someone help me understand why it works this way?

I'd think the point is to make it difficult, but neither overwhelming at low levels, nor trivial at higher ones.