Bret Contreras and Dean Somerset have both written about the possible benefits of the leg press in general.
I general suggest using a full ROM (full contraction to full extension) on most exercises exercises for most people. "Deconditioned" and "injured" would be taken on a case-by-case basis depending on their specific issues/limitations.
With leg presses, squats, or any lower body exercise, It's possible to lockout without exaggerating knee stress. It's not necessarily either/or. But if the hypothetical client has pre-existing knee issues, then it's probably best to use a deliberately shortened ROM and/or modify the exercise to preserve and prioritize knee health (possibly choosing another exercise entirely).