The AD applies to all 737s using that same engine: https://www.federalregister.gov/documents/2023/08/10/2023-17...

However, the MAX 8 and MAX 9 had already been certified and delivered before this AD was published, while the MAX 7 had delays in certification.

The MAX 8 and 9 have the same issue[0], and have a temporary exemption with guidance to the pilots on when not to use the deicing. I think the idea is that this is an issue that can be managed, and the cost of grounding hundreds of planes for such an issue is substantially higher than the cost of delaying deliveries for a plane with no existing fleet. That different cost also leads to a different tradeoff for the two cases.

[0] https://www.federalregister.gov/documents/2023/08/10/2023-17...

I hear what you're saying, but "because we have so many of these planes out there" isn't a rationale that gives me a lot of confidence for justifying a waiver. In the grand scheme of things I'd rather see them stop building shitty planes.

But that gets in the way of making the little line on the graph go up every quarter which means top execs don't get as big of bonuses so shitty planes it is!