Looks like the U.S capability to supply Ukraine with weapons is diminishing pretty fast. The U.S. has a lot of quality weapons but quality also means more complex to make, quantity has a quality all its own, so is a problem for the Ukrainians if the Russians grind their forces faster that can be replenish. In the good ol days you would have China flooding Ukraine with cheap affordable easy to made weapons in large quantities, I say Ukraine only because the Russians are to proud to procure Chinese weapons. But thanks to the Americans the Chinese are providing to no one.
Seems like a really verbose way of saying "we are not really sure if we want to keep running low of our own stockpiles should we keep antagonizing China and we don't have the industrial capacity to produce them fast enough either".
The HIMARS entered into service in 2010, with around 540 of them made since then(according to the sourceless claim in wikipedia), so that leaves you with around 4 HIMARS a month. Of course, this is all just baseless ballpark speculation but if NATO can only produce between 30.000 to 70.000 rounds per year of something as basic as 155mm munition, big ticket items probably aren't that high on the output list either.