I thought you were pointinging out the design issues associated with pressure drops in the strainer basket.

The thruhull screens have between a 50% and (say) 1/3 free area. The velocity through that fitting is much higher than through the basket in the strainer. I thought was to allow the gunk to settle-out.

The total free are of the holes in the basket must be a multiple of the 1.5" diameter hose -- (which would have a cross sectional free area of 3.14*(.75^2) or, say, 1.75 Square Inches.

The strainer basket is also designed to function after it's done a bunch of work (i.e., it's pretty filled-up with stuff).