As for their original post, it is true. If your rating is pushed down a tier by the squish, you remain in the same tier until the next week.
Here's a specific example:
Suppose that you are at the bottom of Kyber 3. To remain in Kyber 3, you need to go 2-1 in the next week of GAC. If you go 1-2, you fall to Kyber 4. The squish doesn't change that because they don't immediately drop you to Kyber 4 because of the squish. After the squish, your rating is technically Kyber 4, but they will let you play as Kyber 3 for that week. If you go 1-2, then you will drop to Kyber 4. But, that was going to happen even without the skill squish.
Same thing applies at the top of a tier. If you're at the top of Kyber 3, you need to go 2-1 in the next week to move up to Kyber 2. The squish isn't large enough to prevent you from moving up a tier in the next week.
They original post never said anything about long term effects just that the squish wouldn't immediately hurt you, which is true. But, the skill squish will push people down tiers and leagues in the long run, it's simple math and someone could argue that it's so obvious that it doesn't have to be explained.