That’s principle of least action. This is principle of least nuclear motion. Different thing.

https://www.sciencedirect.com/science/article/abs/pii/S0065316008601173?via%3Dihub

In many acid-base reactions, the structure of the transition state greatly resembles that of the reactants; very little atomic reorganization is required.

In nucleophilic substitution (and other) reactions, there is re-organization of the atoms in the transition state versus the starting materials. That re-organization requires more energy.

That said, I should probably re-write this to clarify.

Grignard reagents add to the carbonyl – irreversibly. Hydroxide can add to the carbonyl to form a hemiacetal but it is reversible, and eventually deprotonation occurs to give the enolate.
With Grignards, deprotonation at the alpha position only tends to occur when there is a lot of steric bulk around the carbonyl carbon. The C-H bond has to be oriented at 90° in order for deprotonation to occur, otherwise the resulting carbanion won’t be in resonance with the carbonyl pi bond

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Any time you form a carbocation, watch out for rearrangements.

Hi, if you deprotonate C-H adjacent to a ketone, the carbon will not be sp3 hybridized for long. It is energetically favourable for the carbon to re-hybridize to sp2, which puts the lone pair in a p orbital and can then be conjugated with the p orbitals in the C=O group.

It’s this atomic motion which makes deprotonation of C-H “slow”.