Indeed. Though on the other hand the moves are irreversible but reversible...
Whilst the government hasn't said as much, there is nothing to prevent them from bringing forward the date for each stage of lockdown easing, especially if the government finds it politically expedient to do so.
I know they said no earlier that April 12th, May 17th, June 21st..., but there is definitely some slack built into this timetable which allows for unforeseen delays. For example, the current target for vaccinating the top 9 priority groups is April 15th. But at current rates of vaccination, even allowing for second doses being administered, it is entirely possible that this target could be reached before Easter.
If this were to happen, the government might use this as a justification for bringing forward each reopening by at least a week.