I don't think so ...... to me "off grid" requires some method of power generation (for normal non-emergnecy use) as the place isn't connected to the electrical power grid, where homesteading can include locations that are tied to the larger electrical grid. Likewise living off grid could be done by buying most/all food, whereas homesteading means growing both plants and animals for personal consumption (at a minimum).
So to me they're not the same thing, but there can be a lot of overlap. Depending on the location a combination of off-grid power generation and homesteading may be required due to the remoteness of the location ...or it may just be done for personal preferences to varying degrees of either (or both).