3135/2235 Modernized to the 3235/2236

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I always viewed the men's 3135 and the lady's 2235 movements as their opposite gender equivalents. Each are a basic date movement and have about 48 hours power reserve.

The newer versions of these movements--the 3235 and 2236--have been out for a couple years and are slowly making their way into more references.

The new-generation 3235 has a 70 hour power reserve--22 hours longer than the 3135.

The new-generation 2236 has a 55 hour power reserve--7 hours longer than the 2235.

Why didn't the power reserve in the new-gen 2236 increase more than just 7 hours from the previous-gen 2235?

Is it because Rolex didn't put as many technological advancements in the 2236 as in the 3235, or is it because the small size of the 2236 precluded Rolex from increasing the power reserve any further?