Firstly, well done for being approached... a sign you've caught the attention for good reasons.
Think of it as a county-level CORE and what is really them finding a group of officials that they think have at least two promotions in them (which requires resources from them, so respect that in return), so here's a test of those variables wholly in your control as to whether you'd be suitable to operate in the NLS. Availability, commitment, fitness, knowledge of law.
All four of those are in your control. If you can't do every other Saturday cos of a job, someone else will. If you don't reply to emails within a day because you're commuting and need to walk the dog after work and have a kid, someone else will. If there's an emergency and you haven't closed the date but you're going to Lidl so can't cover that game tonight, someone else will. If you've over/under-trained or mis-managed an injury so aren't fit enough, someone else is. If you don't know what restart is correct after a 1/1000 incident, someone else will.
Likely be assigned into smaller groups with a coach who can help you meet the expectations of these things at higher levels, while developing your on-field competency. If you trip up, there's a nudge in the back to do better. If you make excuses, there's wobble of your head that you don't need to be good enough, you need to be better. A coach, a tight-knit group, access to your RDO and mentors, and it will open an extra door that someone else may not have.
It's an investment from the county into you and your development... so be fit, be available, be flexible, have your admin in order, and know Law... and this is their opportunity to mould you into meeting those criteria - again I stress these are your problem - and you can slip-up without season-defining consequences. It'll have a bar to entry because you need to earn it. The RDG isn't a continual test, but if you do what's expected of you and engage then it'll develop you towards understanding the expectations even higher-up that - to use a metaphor - you need to be this tall to join this ride... and if you're not, others will be.
TLDR: Is saying no better than saying yes.