The short answer is your cabin steward gets the $1.75 for a total of $4.00 for you. Most likely, they do not get the gratuity based on hours worked but by person. They visit your cabin more than once a day.
If they normally service 40 people in 20 cabins, but only have 20 people in 10 cabins, their share of the gratuities is likely much less. Perhaps Princess gives them some extra compensation in an attempt to help a little.
The Steward also make a lot of money from the additional gratuities from passengers and they have less opportunities for the extra gratuities due to the lower passenger counts.
This is why during these times, I have become an even more generous tipper. (Cruises and restaurants). I try to make up some of the difference as I appreciate the fact that they are providing a service to us during these very difficult times.
I believe I clearly understand your question and I hope my answer is clear.