RAW this is incorrect, however its the way everyone plays it so its irrelevant.
The Sequencing rule on p57 of CA2021 isn't about priority, its about the order you apply the rules in, which is why you see a lot of people say "cant" > "can" because rules are still applied - you don't just ignore one of them and prioritise the other.
This would mean that "can't" always removes the dice from the pool being resolved before or after you resolves the "can" rule. Regardless of the Sequenced order you resolve them in so you would always end up at the same result as you have to consider both rules.
ie if Transhuman vs Poison had the same wording, attacker gets to pick the Sequence but the Transhuman ignoring 1-3 will always remove the dice of value 1-3 from the pool at their step, regardless of whether you apply that rule first or second.
However, the 40k community at large decided that rather than "sequencing" and still forced to apply both rules, they'd give the attackers rules "priority" and ignore the defenders rule altogether - which is not RAW on how the Sequencing rule works.