If you turn on the signposts by executing View > Signposts > Hide Signposts, you can see the hidden items which give the illusion of smoother playhead motion in the second and third flows.
The tempos in the three flows are dotted quarter=60, dotted half=60 and dotted whole=60, so each repetition has a tempo which is twice as fast as the previous flow.
The second flow begins with the time signature 9/8,18 to create a bar which has a duration of 18 8th notes. The next bar has the hidden time signature 9/4. Every voice in every bar in the second flow has a hidden tuplet which allows 9 8th notes in the time of 18.
The third flow begins with the time signature 9/8,36 to create a bar which has a duration of 36 8th notes. The next bar has the hidden time signature 9/2. Every voice in every bar in the third flow has a hidden tuplet which allows 9 8th notes in the time of 36.
Because the bars in the second and third flows have two and four times the duration of the bars in the first flow, respectively, note spacing changes are used in the second and third flows to maintain the same bar widths as in the first flow.