From what I am seeing in my literature review, it is safe to engage in early mobilization within 24 hours after ischemic stroke if no tPA is administered. If IV tPA is administered for an ischemic stroke, it is best to wait 24 hours to monitor for hemorrhage. 
After subarachnoid hemorrhage, mobility can be initiated 24-48 hours after aneurysm treatment. After intracerebral hemorrhage, mobility can be initiated 24 hours after stable ICH volume. 
There is evidence that early out-of-bed mobilization within 24 to 72 hours of ICH may improve early functional independence. 
Admittedly, acute care is not my area of expertise. I do not have direct acute care experience since my residency program and am open to any resources you have found to be helpful in your studies!
1. Physical Therapy Case Files Acute Care by Erin E. Jobst
2. Olkowski BF, Shah SO. Early mobilization in the neuro-ICU: how far can we go? Neurocrit Care. 2017;27:141-150.
3. Yen HC, Jeng JS, Chen WS, et al. Early mobilization of mild-moderate intracerebral hemorrhage patients in a stroke center: a randomized controlled trial. Neurorehabilitation and Neural Repair. 2020;34(1):72-81.