Likely, ramazan is remembering the spotlight mentioning higher chance of getting gold+ rarity females (or was it platinum?). However, that had just been a somewhat poorly worded way to state that all female units were on spotlight, so you would be fairly unlikely to get male units. It did not alter the chances of getting any given rarity, and like all spotlights, did not extend to any type of summoning outside premium summons.

That said, on the topic of saving or expending the crystal pieces, it can sometimes be worth holding off on using them if you know a new gold or silver will be added to the pool soon. I myself am presently hoarding mine in hopes that soon Nutaku will take over development and add in the various skipped silvers.