This is also true for any high leg system like a 240/120 delta system. 240*240=57600, 120*120=14400. 57600-14400=43200. The square root of 43200= 207.84 and we round up to 208.
Once under load the voltages will change on any system be it delta or wye depending on the load applied and the configuration of the load three phase or single phase.
Also remember that the neutral of a wye system where nonlinear loads are served there can be no reduction of the neutral conductor due to the possibility of high harmonic currents on the neutral conductor.
Edited the second time to add;
The laws of physic are not up for debate. Math does not lie.
If you are seeing 219V on the high leg to ground then the 120/240V nominal system is also high they would be 126 phase voltage and 252 line voltage.