Being that the secondary as pictured is a single phase 240 volt winding there is no way that anything in that picture can be out of phase except for the primary to the secondary. As the picture shows at 1 on the primary is a dot and on the secondary the dot is 180 degrees displaced and is found at 7 and 5.

I order for the two 120 volt windings to be 180 degrees displaced then the dots would be at opposite ends or in the center together.

Considering one quarter of a football game where one team is trying to take the ball to one goal and the other team is trying to get the ball to the other goal both teams are running at 180 degrees against or out of phase if you please.

In a single winding or even the two windings you have posted the current will flow through the winding from one end to the other end and the laws of physics will not allow those electrons to oppose each other by being 180 degrees out of phase.

If you cannot grasp that what you are seeing on the scope is both ends of the sine wave looking toward the middle then there is not much hope of you ever making anything but a helper. Being able to figure the arc flash abilities of a panel would be totally out of the question.

Take a three phase 240 volt delta transformer and tap the center of one winding. From the corner of the tapped winding to the tap will be 120 volts. From the center tap to the odd winding will be the square root of the voltage from the center tap to the odd winding squared minus the square of the voltage from the center tap to the end of the winding that is tapped. 240 times 240 equals 57600. 120 times 120 equals 14400. 57600 minus 14400 equals 43200. The square root of 43200 equals 207.84.

A short cut one can take is to multiply the 120 by the square root of three which will be guess what, yep 207.84

Should we use this 240 volt three phase to power a 10 kw heater the amperage draw would be 24 amps. How one might ask. Multiply 240 by the square root of three to get the three phase voltage of 415.

I have been teaching electrical theory for a decade and a half, a lot more time than it takes to get a PHD.