Yes, but softness is irrelevant here. For example, thick plastic is what you may call “hard”, but thin plastic as in Saran Wrap is quite soft. Chemically, they are virtually identical. Softness as opposed to hardness (what we prefer to call “modulus”) is a physical property of the polymer, but so are tensile strength, softening point, oxygen flux and a bunch of other properties that exist but are irrelevant to the halachic discussion.
The point here is simple. Dirt, protein, lipids, junk, what have you, adhere to the surface of the lens, but do not penetrate it. This adherence is no different than chulent sticking to a plate. If I can clean the plate with a cleaning liquid, I can clean the contact lens.
I am willing to venture that the poskim did not differentiate between ionic and non-ionic surfaces, or what technique was used to put on a hydrophilic coating, etc..These issues would make the discussion more interesting, but would not change the conclusion.