Both are still 55 h/w of grinding. Worrying about WLB and not keeping your head down would be, "I'm off the clock, no more working on anything related to work in any capacity today".
Prepping for interviews outside of work would still very much count as "grinding" in my opinion.
55h/week job because time sucked up by lengthy meetings and status reports.
40h/week job then spend 15h/w spare time learning algorithms and design interviews.