not sure why that 4444 para was brought up here
Brought up here, I guess, because your ANSP's standard sounded like it might be based, in part at least, on that procedure. Your original enquiry was about 'separation' between two pieces of airspace - which is not well standardised - and something that might be relevant to the discussion. I simply pointed out that the Doc 4444 reference was based on certain assumptions which may not apply to the situation you described.
But the criteria used by your ANSP is interesting - does it actually provide assurance of true separation between aircraft operating each side of the reserved airspace boundary?