Neither this article, nor the actual paper it is based on (https://www.nature.com/articles/d41586-024-02731-9#:~:text=T....) has any mention of exercise, and the title here seems to be editorialised to add in "Metabolic byproduct of anaerobic exercise".
Just because lactate is produced from anaerobic exercise and this study found that lactate was used by the cancer cells, doesn't automatically follow that the cancer cells can use the lacate produced from exercise.
They're probably talking about the Warburg effect, not exercise. The body is complicated and just because exercise can produce lactate doesn't mean it has anything to do with this.
Just because lactate is produced from anaerobic exercise and this study found that lactate was used by the cancer cells, doesn't automatically follow that the cancer cells can use the lacate produced from exercise.