This is a really good question.
Without the Toyota design specs we can't really know for sure.
But in the engineering world we confront these circumstances all the time.
When we perform a competitive product analysis, we may not know what the competitors specs are but we can make observations based on the product that the competitor produces.
So let's make two simple observations of the Toyota OEM cartridge filters.
1. Conventional media
2. No end caps
Based on these two observations, we can conclude that these design elements are appropriate. We can bolster this conclusion by observing the number of units in operation (installed base) and look for the number of failures in operation.
Toyota cartridge filters have little to no history of wide scale failure in operation.
Therefore we conclude that the design elements (conventional media and lack of end caps) are appropriate for the application.
As I said previously to @ZeeOSix
I'm done here.
Have a great evening and weekend!