I have been walking my dog these three years.-- OK

He has been playing at Wimbledon since he was 18 years old.-- OK

A private English school's website in Japan says the above expressions should be changed to:

I have walked my dog these three years.-- OK

He has played at Wimbledon since he was 18 years old.-- OK

The site explains that the present perfect progressive form cannot be used to describe people's habitual activities unless the activities have been in progress without a break.-- Not true; it merely emphasizes the durational quality.  However, I can see that that ambiguity could arise; in that case, it would be wise to choose the non-progressive

.

Mister Micawber

“

I have walked my dog these three years.-- OK

He has played at Wimbledon since he was 18 years old.-- OK

 

The site explains that the present perfect progressive form cannot be used to describe people's habitual activities unless the activities have been in progress without a break.-- Not true; it merely emphasizes the durational quality.  However, I can see that that ambiguity could arise; in that case, it would be wise to choose the non-progressive

”

I forgot to ask you one more thing.

You wrote "ambiguity could arise."

Do you mean "He has been playing at Wimbledon since he was 18 years old" implies that he will continue playing tennis at Wimbledon while "He has played at.." impies that he may stop playing at Wimbledon in the future?

Mister Micawber

“If ambiguity arises about 'unbroken habitual' because of use of the progressive, then use the non-progressive form.  In your examples, no reasonable mind would expect the dog-walking or tennis-playing to be interminable.”

Thank you. I understood.