This interaction between the Extensions Manager and the System 7.5 Update 1.0 installer is normal (that is; it functions as it was intended to). Before installing System 7.5 Update 1.0, open the Extensions Manager and choose the "System 7.5 only" extension set. This will help to ensure that any disabled extensions are updated, when the System 7.5 Update 1.0 is installed.
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