Training ideas are only useful when they still make sense on a real day. Weather, fatigue, terrain and the rest of the week matter more than making a screen or a plan look perfectly completed.
The question behind the benefits of zone 2 work is what changes in practice. The useful answer is usually found between build aerobic work without racing the day and keep the ego out of it: the point where a broad idea becomes a choice that can be made, observed and revised.
A steady conversational effort allows useful time on feet or on the bike without the recovery cost of another hard session. The exact heart-rate boundary varies, so effort and context still matter.
Easy aerobic work can sit between quality sessions, extend endurance and create consistency. Its value is not that every minute is perfectly inside a device-defined zone; it is that the session remains genuinely easy enough to repeat.
Use more than one signal
Heart rate can be affected by heat, fatigue, terrain, hydration and sensor accuracy. Combine the device with breathing, perceived effort and the purpose of the day.
The pace may look slower than expected. That is not a failed run. A controlled day that protects tomorrow’s training is doing exactly what it was meant to do.
The purpose of the session matters more than completing every line exactly. A useful plan can be shortened, slowed or moved while still protecting the reason it was included in the week.
That is the standard I would use when returning to the benefits of zone 2 work: keep the reason visible, make the next decision small enough to understand, and leave enough evidence to know whether the approach is still helping.