My basic understanding is:
If the actual conditions are above the minima, but below the lower safe, instrument approaches will be in use.
This use of instrument approaches will reduce the rate of arrivals due to slower speeds down final, plus the preclusion of visual separation.
This reduced rate of arrivals may cause delays (demand v supply) even though the conditions are relatively benign, at that instant.
If the original forecast conditions (TEMPO or INTER) gave cause to carry holding fuel in excess of the current delay, a holding fuel NOTAM will not be issued. (even though the cause of the delay at that very instant is not the TEMPO or INTER)
Clear as mud?
In other words, dont expect a NOTAM for holding fuel if the forecast conditions gave rise to the possibility of holding in the first place. (ie: below the absolute lowest minima) The grey area comes when differing aircraft can make the approach in marginal conditions, or when it comes to clearing the log-jam when the weather improves (as I think somebody mentioned on page 2)
Cheers,