Could you please tell us how you know this information?
Common sense, agreement with general reports on the net, and looking through various Epson service manuals.
Experience and Epson manuals tell us that the only way to check for a clog is to print from each nozzle and verify that ink hit the paper. The printers that self test for clogs do it by printing test patterns and then looking at the paper to make sure the patterns printed correctly.
If the printer was able to measure ink flow, then there would be no need to waste paper on a nozzle check. The printer could spit ink directly into the spittoon, and verify that the ink flowed for each nozzle fired. The fact that Epson includes an optical sensor for self checks is evidence that the printer can't measure ink flow. In fact, the printer wouldn't have to waste ink in order to check the nozzles. If the printer could measure ink flow, it would know there was a clog anytime the requested ink amounts did not match the measured ink amounts.
If you look at the various service manuals you will see that there is no part of the printer that actually measures ink and reports back to the controller. Furthermore, there are no failure modes described related to failures to measure ink flow.
If you do a web search, you will find that it is possible to accurately measure the amount of ink in a cartridge by weighing it. You will find many reports of people who have battled with stubborn clogs, only to end up with mostly full cartridges that are unusable as their controller chips think they are empty.
I would be much happier with a printer that did measure actual ink usage. It would never require a separate nozzle check. It would automatically detect clogs during the normal course of printing. When clearing a clog, it could detect when the clog was cleared, and stop the cleaning process when the clog cleared, as opposed to mindless wasting ink in the hope it had spurted enough.