There's usually a difference in top address line(s) and !WE pin, since EPROMs have a programming voltage pin that wast majority of Flash chips don't have and some different ideas about if a write strobe is needed or not.

To use Flash in place of EPROM you have to make sure that the !WE pin is in high state and relocate address pins if entire address space is required. In the example with 1MBit EPROM and 4MBit flash, you just mirror the image to fill entire flash, then the top address lines stop mattering and only !WE needs to be looked at more carefully.

EPROM in place of flash has the same problem, the top address lines need relocating if entire space is necessary and some attention is needed about what state the VPP pin needs to be for normal operation. In most cases it needs to be at 5V level but I have seen EPROMs that want it to be at GND instead. !WE state may or may not be important but in general it should be in high state as with flash chips.