In the press release they say they are closing it to make the crossing safer, possibly barriers and lights,
In the web page that the press release links to they say just chicanes to force people to look both ways.
And the station closure is planned for far longer than the level crossing works are expected to take so this can't be used to justify the closure.
It's not the most road accessible place and I am guessing quite a bit of ground work needs doing before the platform can be added. The days of laying out a few sleepers a la ADNR have gone!
OK let's assume that when they cleared and flattened the area beyond the existing platform that was just part of the electrification and maybe tracklaying worked and not the ground preparation that it looks like.
But - when they did do all that, they did it without a long station closure.
Have a look at Google Maps. There is a road leading right up to the railway boundary - I'm pretty sure they made a gap in the fence for access to carry out the previous work.
But OK maybe now they've been refused access and will have to work another way. But I still don't see why that involves closing the station completely.
Look at Danescourt on Google Maps. It sits in a cutting and I'd happily describe that as not the most road accessible place yet somehow they managed to extend both platforms without closing the station.