Yep to a small degree. What they do is reduce reflectivity of hard surfaces. Floors, tables, walls, glass, certain furniture like leather couches. Tossing rugs on the floor right in front of the subs will help, big fluffy pillows in Corners and throw blankets over reflective furnishings. All little improvements that can add up and help make the room less reactive to sound bounce.
I thought that we were talking about a bass trap, and bass, or at least that is in the title.
While agree that a rug, curtains, and plants absorbe and scatter sound in the higher frequencies… those things are not known to be good at bass trapping.
Secondly the pressure zone is against the surfaces of the room, like walls, ceiling or floor.
The zone where velocity absorbers work are well away from the boundary condition where the velocity, by definition must be zero.
A rug is in the pressure zone, and it is truely not intruding upon the velocity region when it on the orderr of a centimetre think, and the wavelength is 10-25, long.
I agree blanket or a pillow is thicker, and will start to actually work in the upper bass. Especially if it a bit off the wall like on a bookself or curtain rod.
I have never seen plots of RT60 of room with and without a rug, and noted seeing subwoofer freqs shorten.
The physics are against it in the subwoofer region where the OP is working.
I believe that we are doing a disservice to suggest to the OP to use a rug for subwoofer bass.
But a rug is a good idea in general… just not as main treatment for sub freqs. (IME).