overestimation of MET (Metabolic equivalent of Task) during pool swimming

Hi everyone, I'm an amateur backstroke swimmer and therefore have a very slow pace (average SWOLF of 68 over a 25-meter distance). Although my Apple Watch S11 correctly detects my swimming style and the number of laps I've completed, the estimate of active calories burned is too high, almost double what I expect. Analyzing my training data in detail, I saw that the algorithm estimates an average MET effort of 10.5, which according to the tables is equivalent to vigorous swimming (my value should be around 4.5 METs). Is anyone else experiencing the same problem? Do you have any advice? Thanks.