I think it becomes more and more known that there is a group of applicants that think that as soon as they got approved for the visa all requirements end and they can just stay in the country for 5 years.
DTV is not meant for continuous stay, only for periods you do remote work or attend soft power activities.
It looks like they now want to make aware applicants of this.
The only correct answer is to tell your plans, how should we know what your plans are.
You can explain what you want to do after the current activity ends, and when you don't have plans for that period, you don't need a visa for that period.
Because we do not know why you were reacted it is difficult to say it that is unfair.
I do not see they encourage you to apply again, so if I were you I would try to find out what might be the cause for rejection. Can it be wrong filled information in combination with your passport data?
Or they just ask all foreigners for proof, just like in the beginning of this year all Thai people needed to show the phone number for the app is registered on the same name ast the bank account.
What wouild be ridiculous? Tha a visa application is cancelled because the applicant does not follow the rules? Visa tourism has some risks because it is always uncertain how long an application will take.
Therefore the advice is to apply where you live, and long enough before travelling to the country.