I have a feeling, they mean production inventory, i.e. raw materials to be able to produce.
We went into overdrive, when the first lockdowns occurred, but at some point, we had to throttle back, because the raw materials were just not deliverable, or the timescales had extended. That meant scaling back production volumes, to ensure we had enough raw materials to keep the plants going. When certain chemicals became available, we'd order as much as we could store, to ensure we had supply for production going forward, with no certain availability or delivery dates, when the next wave of lockdowns came.
It is a juggling act, ensuring enough raw materials are coming in to be able to produce, and having enough orders going out, to justify the buying of the raw materials. Raw materials sitting around in the warehouse are a cost to the business and the last 40 years or so, it has all been about cutting those stocks down to near zero in some industries.
For example, automotive get tyres delivered throughout the day, usually going from the trailer to the production line and straight onto rims, which go straight onto the vehicles running off the line. There might be a couple of hours of inventory, but not much more. If the trucks stop coming, production stops. Obviously, not all parts can be delivered that way, but for bulkier items, JIT (Just in Time delivery) is used as much as possible.
I worked on systems in the late 80s and early 90s to optimize JIT production and logistics, it is actually a fascinating problem; but as the last year shows, if supply dries up, you are royally screwed.