Maybe this....
What appears to us to be a 15 minute change between the two watches could actually be a 45 minute GMT offset after reading this.
"While most time zones differ from Coordinated Universal Time (UTC) by a number of full hours, there are also a few time zones with both 30-minute and 45-minute offsets."
After looking at this image again I see what appears to be close to a 30 minute difference between the watches. The hand to the right is either Brand, Slayton, or Stafford and the watch is mostly likely set to Houston time. It is the same time seen on Leonov's signing hand watch 2:25. The other two are off by almost 30 minutes. The Soviets could possibly be setting their watch to a time zone that has either a 30 or 45 minute offset. That's the best I can come up with so far.
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