Technically true but they still are getting the ESIM's IMSI and the phones IMEI. So, while true, it does not get the MSISDN (your phone number, it's still getting identification info that can easily be use to track a phone geoloc and use patterns.
That info can be used to id you as well. BTW this effect of not revealing phone number while roaming is not some unique feature of Silent.nnThat is standard function of a phones sim in roaming on a different local providers system. Any phone in roaming works that way.