No sarcasm intended. Maybe English humour. If you perceive it as sarcasm I shall stop here and now.
CDAs are the ideal but not always possible for a number of reasons.
What I am saying is that (from my time doing it) if an operator was known to be 'ponderous' it may be that they be given 'approximately 20 miles' when the range more likely greater eg. maybe 24. The psychological effect usually secured prompt response and useful performance which would avoid wasted final approach spacing rather than a request from the pilot for extra miles.
w.r.t. 27s v 09s the RMA for 09 is less constrained and therefore provides more flexibility for changing the sequence in order to maximise runway capacity. Such order changes will, of course, change distances to touchdown.
As in life, if one 'dilly-dallies' one is likely to be overtaken.... (not sarcasm)