If they plan years in advance then they should have years of work in the pipeline - it doesnt make sense hence likely an excuse.
Yes they'll have work in the pipeline, but that is what it is, a pipeline.
There will be parts of the company that will be working on existing projects for the next X years, but there will also be parts of the company that need to get the next job lined up and start on that.
If there is uncertainty about the future projects, or you fail to get jobs you expected to win and it looks like the conditions are going to make it harder to get replacements, looking long term you might want to cut staff who are underutilised at the moment (but were expecting to be fully using again soon), or cut hours so you retain the staff for as long as possible.
Cutting staff means losing the expertise completely, putting them on shorter hours means you can hopefully ramp up faster when conditions improve (and it's kinder on the staff).
IIRC it's what a number of businesses tend to do if there is a major downturn in their market for whatever reason, as if your staff need specialist qualifications and experience it's much harder to recruit replacements.
It's also worth noting that cutting fixed hours early (and any cost cutting measures that don't affect your ability to deal with your current workload) tends to pay of later.
A little like if you are self employed or on a short term but well paid contract, you don't wait until you've got no work and no income to cut your expenses, if you're sensible you'll cut back a bit where possible before you run out of work so your savings last longer.