Yes of course it was intended because we have known what makes novel zoonotic viruses deadly for over a century. Epidemiology is not a new science.
The science behind this drug is new. The earliest paper I have read about the concept dates to 2016 however work on it ramped up when COVID-19 hit. I cannot say that the drug will be successful in forcing the mutations which result in the virus being both more contagious and way less deadly, but I can say that what you seem to be concerned about is already occurring in the wild in Sars-CoV-2 and is the reason why COVID-19 is becoming now like the common cold.
Here is a link to the latest paper I have read about it from March 2023:
https://www.sciencedirect.com/science/article/pii/S2589004223002870
Please correct me anyone with my thanks. I am no expert. I can accept how a mutation in the ExoN domain might deactivate nsp14 which in turn will result in rapid mutagenesis, but how you would make that happen by giving somebody a drug is way over my head.
Correction.
I clicked the links within the article and it looks like they meant their drug to work like a standard anti-viral and the mutagenesis is an unintended consequence.
I will maintain that mutagenesis and natural selection is exactly what we want.
Please correct me with my thanks.