I'd say yes.

Many of the weathering powders come in a form that looks very similar to the crumbled sample and they work fine.

Voice of experience

Several of the colors in a set I bought looked like your photo.  BTW, I complained and received a partial refund.

If you try to use them the way they are lumps will stick to the applicator and make a mess.

Two ways to salvage them.

1.  Carefully apply 91% isopropyl alcohol and stir until all the bits are dissolved into a creamy paste.  Break up the lumps.  Let it dry.  Downside is it may crack as it dries and the surface is not smooth but they still seem to work fine.

2.  With some smooth and flat tool, I used a small pallet knife, pack it down.  I've not been able to get the whole surface packed but I use it from part that is packed and repack once in a while.

Absolutely !

Yes without a doubt !  Sometimes I even scrap some to get mine like that .. for some applications (ex, mixing colors).

It's still useable

I dropped one of my PanPastels and was left a mess similar to yours. I salvaged it like railbirds #2 option but I used the flat top of a model paint bottle to compress everything back to as close to smooth as possible.

Thanks everyone

I will try to pack it to a smooth surface.

Pierre-Yann