Yes -- the cotton-twill is a heavyweight outerwear cloth (450gsm or thereabouts). Typically we make trench coats and work jackets with it.
The cloth is intended to soften and adapt with wear. Washing it certainly will soften it, but probably best to wear it a few times, first, before doing so. I have a trench coat in the same cloth myself, which has been worn for a couple of years, and it is now the softest thing around -- sort of like how raw denim softens up to an unrecognisable degree after a year or so. Its brushed handle, already quite soft, also becomes more exaggerated over time; a customer the other day mistook my old trench for moleskin -- which was a bit of a stretch, I must admit, but still: gives you an impression the degree to which is mellows with time.