It looks like the line's lifetime is forced to the default line lifetime of one second if the provided lifetime is less than zero, which would be the case if calling the function with just enough parameters to pass in true for bPersistentLines.
This appears to be a regression as the issue does not occur in 4.19 (CL 4033788), but does occur in both 4.20 (CL 4369336) and 4.21 (CL 4489857).
Result: The drawn lines are removed after the default line lifetime (one second).
Expected result: The drawn lines are not removed.
Head over to the existingAnswerHub thread and let us know what's up.