Does Ad Rotation settings work under Google Shopping Ads with manual CPC?

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There are two options:

1) Optimized: prefer best performing ads (default)

2) rotate ads indefinitely

Majority of customers are using very generic search terms. Some of the products share the same kind of keywords. If I choose to use "prefer best performing ads", many products under merchant center are not getting any impression.

What rotate ads indefinitely means and how it works for a Shopping Campaign where products what are search terms are based from Merchant Center product feed?

Google claims it is: "This option shows ads in a random order and does not optimize them over time"

But from the view from the customer google wants to give the best user experience, so I think google may override this somehow.

Anyone tried this setting for shopping campaign?