I agree on everything that you posted Davolijj...but remember there is the approach sequence then there is the landing sequence. The tower may have other traffic in the sequence such as T&G’s etc. that approach does not know about there fore the landing sequence may be much more different than the approach sequence, in Boston’s case...T&G’s may not be the reason.
From the Good Book (7110.65P)
Note the note
at the bottom.NOTE-Landing sequence number is optional at tower facilities where arrivals are sequenced by the approach control.
To elaborate on your answer:
Part of the question was “why do they sometimes state the runway and sometime don’t”. Let's go back to your "bible of ATC" when more than one runway is in use:
3-10-5. LANDING CLEARANCE
a. Issue landing clearance. Restate the landing runway whenever more than one runway is active, or an instrument approach is being conducted to a closed runway.
CLEARED TO LAND,
RUNWAY (designator) CLEARED TO LAND.
Another reason why they don’t issue the landing clearance right away and say “continue” or “expect late landing clearance” is a delay tactic to avoid clogging the frequency with required information such as exchanging traffic if you clear an aircraft to land and you have one in position that has not been clear for takeoff yet...i.e. paragraph b below:
b. "USN NOT APPLICABLE." Inform the closest aircraft that is cleared to land, touch-and-go, stop-and-go, or unrestricted low approaches when there is traffic holding on the same runway.
"Delta One, cleared to land. Traffic holding in position."
"Delta One, runway one eight, cleared to land. Traffic holding in position."
A clearance to land means that appropriate separation on the landing runway will be ensured. A landing clearance does not relieve the pilot from compliance with any previously issued restriction.