The WMS GetFeatureInfo text/html format doesn't have any special treatment for date \ times and simply do a to string regardless of the timezone or time format.
It should also be possible to control if GeoServer will or will not take into account the the time zone when encoding date \ time attributes using this Java property:
-Dorg.geotools.localDateTimeHandling=true
Since text/html format is handled by Freemarker template engine, a version upgrade is required for fixing this.