Agree. We had one or two credits per cruise, depending on length if I recall rightly, and they were converted to points when it changed over around 10 years ago, but both were kept independent of the line you cruised.
From X’s section in past cruise history online:
Before November 25, 2013 members earned one loyalty credit for each of the following scenarios:
Sailing on any cruise
Sailing on any itinerary of 12 nights or longer, including Cruise Tours (applicable to sailings on or after January 1, 2003)
Sailing in a Concierge Class stateroom, Aqua Class stateroom or Suite (applicable to sailings on or after January 1, 2004)
On November 25, 2013 Captain’s Club converted from awarding credits to awarding Club Points based on number of nights and stateroom category. Credits earned prior to this date were converted to Club Points at a rate of 1 credit to 30 Club Points.