Does it matter what order your keywords are uploaded to iStock? When you use Lightroom it puts your keywords alphabetically and so when uploading directly to iStock through Getty you don't get to re-arrange your keywords and when I use DeepMeta I cant see how to re-arange my keywords in the order I want them other than type them in from scratch?

I'd say no... the way the agencies organize the keywords I doubt makes any difference for SEO/discoverability of your images/videos...