It's really simply: dont harrass people. That's the main problem yoshi-p has and it is only semi related to third party tools, which are by his own admission a huge grey area. He puts out a blanket no but refuses to specify what counts as third party program and what doesnt. Simply put, it's not worth having that discussion. This approach by the devs is honestly not bad, they look at the actual issue related to ACT, harrassment of players over damage numbers, and not any and all third party tools.

Dont forget that he's also telling the people who dont use third party tools (again: term with a huge grey area) to not worry about it. Dont start report wars, dont be vindictive about it.

There are downsides with this approach of course as the game by itself doesnt make it easy to see if you are improving or not as even an official ACT but only about your own damage numbers got a hard "never" from the devs so that it cant be used to gatekeep PFs. Although even that could be side stepped with enough dedication with just ingame tools. What's functionally the difference between a PF saying "provide proof of your dps numbers being high enough" and "provide proof you can clear a certain SSS dummy with atleast x seconds remaining"? There's also another thing, if you know the job someone is playing well, you really dont need ACT to see if they are performing well or not.

This general no is not as clear as some people think it is, simply because yoship refuses to specify what falls under it and I dont blame him for it. Harrassing people over their performance is not stopped by going after third party tools, it's stopped by punishing people who harrass others.