Possibility of carbocation rearrangements in SNi reactions

According to several sources, the $S\_{N}i$ reactions follow a mechanism allowing carbocation formation while others disagree. Precisely, for example, according to *A Guidebook to Mechanism in Organic Chemistry - Peter Sykes*, it states that



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> Whether the breaking of the C-O and the S-Cl bond occurs simultaneously, or whether the former occurs first, is still a matter of debate.
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Thus, it's unknown if a carbocation formation occurs or not. Now my question is if carbocation formation occurs, wouldn't that imply hydride and methyl shifts are possible within the cation? However, in the case when the reaction is concerted, such rearrangements are not possible. Take the case of the following reaction for example,
$$\ce{3-Methylbutan-2-ol + SOCl2 \to 2-Chloro-3-methylbutane (Major)}$$
Is the above more likely or the following after carbocation rearrangements:
$$\ce{3-Methylbutan-2-ol + SOCl2 \to 2-Chloro-2-methylbutane (Major)}$$
Now shouldn't the latter imply the carbocation formation and the former reject it? Which reaction occurs in reality and why is it the reaction mechanism undetermined exactly?


