No, they are not proposing 56 bit key lengths. I understand the key is always 128 bits. They are saying that the entropy should be minimum of 56 bits. In fact the entropy is always 128 bits but this negotiation reduces it because 'some' governments didn't want other governments to have stronger encryption. See [1] page 1050, figure 2.
I don't know how much difference that makes (I am not an encryption expert), but it is a fact that affects your comparison to DES.
No, the article is about KNOB, which allows the attacker to arbitrarily shorten key length. The proposed solution is to have a minimum 56 bit key length, which is still too short.
I don't know how much difference that makes (I am not an encryption expert), but it is a fact that affects your comparison to DES.
[1] https://www.usenix.org/system/files/sec19-antonioli.pdf edit: citation