You’re correct that it’s not grammatically wrong, but a subtle semantic mis-match. Let’s bring in the difference between “every time” and “whenever”. While “when” and “every time” are interchangeable, “whenever” and “every time” are not. “Every time” is exact and without fail, while “whenever” implies unpredictability or indifference to the exact location.
“When (strongly implied every time) I go to the theater (exact location), I get popcorn.”
“Every time (explicitly) I go to the theater (exact location), I get popcorn.”
“Whenever (unpredictable, indifferent) I go to the theater (exact location -mismatch with unpredictability) I get popcorn”
You’re correct that it’s not grammatically wrong, but a subtle semantic mis-match. Let’s bring in the difference between “every time” and “whenever”. While “when” and “every time” are interchangeable, “whenever” and “every time” are not. “Every time” is exact and without fail, while “whenever” implies unpredictability or indifference to the exact location.
“When (strongly implied every time) I go to the theater (exact location), I get popcorn.”
“Every time (explicitly) I go to the theater (exact location), I get popcorn.”
“Whenever (unpredictable, indifferent) I go to the theater (exact location -mismatch with unpredictability) I get popcorn”
Does that make sense?