Given that testing isn't mandatory, thank goodness, then knowing the numbers onboard is pretty much meaningless. Having had Covid last year, and being symptomless I am happy to move on. If you are prepared to go on a cruise then catching any manner of illness, be it gastro or flu or covid, is just a part of the risk. Covid is here to stay. Influenza is here to stay. How much longer can extreme measures like mandatory testing be in place? Wear a mask if you want but in reality that won't stop you catching covid. Or flu. It just minimises the risk.
In many countries now, seasonal influenza is much more prevalent than Covid but no one cares to know.