Two possibilties, one, less likely: typically they work on the bottleneck things first and redeploy the people there.

Two: most likely, an earlier contract to construct the station (and especially for interiors like stairs, it's always a different contract) was cancelled[1] and they have decided to postpone tendering a new contractor for that station, until the nagging land issue is closer to being solved, lest the same issue happen again with the new contractor.

If you meant why can't it be decoupled, well that's because in general some entity in the chain won't give you a completion certificate trusting that you will integrate the two decoupled projects properly later. If you want to make the integration a separate step, no contractor will assume responsibility for it and sign it since the two components are done by others and it becomes a game afterwards of who takes the blame. It's also extremely low margin work. Sometimes, you will see TATA led businesses take the risk and somehow do it, out of altruism towards nation building, but I have not seen any one else do it.

In general the rule with govt contracts is that if there's any problem at all with the contract, all work even if it's unrelated physically speaking, will stop. Because it's related contractually speaking. Such is life.

[1] e.g because the timeline after delays stops being viable for him