advice on change of duty pattern

[not me]

not for me,though involves me in a way

okay so a collegue works a shift pattern
2 weeks on one,2 weeks on the other in rotation

now due to light duties and the like.
the managers want to change this to 1 week on one duty,2 weeks on the other.
now they arent keen on this for various reasons but management are saying thats how it is yadayada

so whats the deal here? its possible this is a temp move but as we know. once things are set in motion it often stays the same