A sensible scenario that can be read between the lines:

Sarin is produced by two chemicals, we'll call them Chem A and Chem B.

Everything is fine, safe, and "proper" as long as A and B are stored far away from one another, in distantly separate buildings.

Weaponised sarin is produced when A and B physically combine, like in a blender (or a whirling missile that slams a glass vial of A into an adjascent glass vial of B).

Placing cylinders of A and B side by side (or in the same building) means that they are no longer "stored properly".

Placing vials of them together side by side in a warhead means they are really, really no longer stored properly.

When the two vials get dropped together in a warhead, then that is when they physically combine and produce the sarin.

Perhaps our latest news reports are that quantities of A and B have been transported into one facility. They "could" still be separated and rendered safe, but it would be kind of dangerous to move them around unnecessarily once they are that close together. In short, there is no reason to go moving them together into one facility unless you intend to weaponise them into sarin.
Just one scenario, but it is sensible, and fits all of the bits of data that we have now.