As the surface area of cement increases due to fineness, contact area for water will be larger. So rate of hydration will increase and we get early strength due to increase in rate of heat of hydration but it doesn’t mean any increase in strength. In similar manner, I don’t think there is any effect of surface area on the amount of CSH gel but rate of formation may increases as rate of hydration will increase.

For more details please refer

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https://www.jstage.jst.go.jp/article/cement/64/1/64_103/_article/-char/en

As the çement gets finer the surface areas increases and the cement hydration process accelerates. The percentage of uñ-hydrated cement also decreased. Overall the C-S-H gel will increase and concrete will become more impermeable.

• The fineness of cement affects hydration rate, and in turn, the strength. Increasing fineness causes an increased rate of hydration, high strength, and high heat generation.
• Bleeding can be reduced by increasing fineness. However, increased fineness can also lead to the requirement of more water for workability, resulting in a higher possibility of dry shrinkage.

The finer ground cement, the more very fine fractions, i.e. the more developed specific surface of the cement, the greater the reactivity of the cement - more hydration reactions occur simultaneously (especially in the initial phase of hydration).

Therefore, among others high early strength cements (marked "R" in Europe - 32.5R, 42.5R, 52.5R) are more reactive.