uk_climber,
You’re correct that cycling offers a less specific workload than running or uphill movement (real or simulated), so if you’re targeting objectives requiring on-foot work, you’ll diminish the returns when on the bike.
That said, using cycling as a means of active recovery (read coach Drew Hammond’s recent article on this) is entirely acceptable and your daily commute can fit into that category provided it remains quite mellow (i.e. sub-Aerobic Threshold). Monitor your overall training fatigue from week to week as you progress your planned sessions, and if you find that the cycling sessions are becoming more taxing, or longer in duration, or if you’re not recovering well from session to session, you should probably start quantifying the daily ride into your overall total and consider pulling back on volume in one area or another to ensure you aren’t over-doing it.
Sam.