Many runners have gone well over 127,000 miles in their lives. A handful have even gotten to 200,000. Ten miles a day for 30 or more years isn't that big a deal if you maintain interest and desire if you're a runner. But ten miles of swimming takes a lot more time than running does so I agree that even 10 miles day for that length of time seems unlikely for a swimmer.
Your last sentence is the key: Ten miles of swimming takes a lot more time than 10 miles of running.
You may be right that a good many runners have done 127,000 miles in their careers but it still seems high to me. I ran from age 14-57. Very low mileage in high school and college (1950s: ignorant coaches and no internet or other info sources) and off and on in early 20s. But very consistently the last thirty years. I doubt I reached 80,000. Gotta check the musty training diaries.
Loved Lurker's response. The first person who replied to my OP asked me to prove she didn't. Lurker proved she didn't run 100/day. He said:
Her PR in the 1500 is 15:52, which means that at her PR pace she could only swim about 85 miles per day if she swam at her PR pace continuously for the entire time.