Yes why wouldn't you be able to ? It's not based on park proximity , only that you bought Genie Plus and that tiems are available. I did this when Maxpass was a thing years ago.
Once you ticket is scanned into the park activated for that day you can book Genie+ from anywhere. It is not location based other than you would have had to enter the gate at some point.
For example you could walk into the turnstile at the Monorail DTD entrance, scan your ticket, turn around walk right back out having never even entered the parks and Genie+ reservations would then be available.
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