There's nothing stopping you from trying, in fact, you could try it, but you'll be running into stability issues because the variation of the output will have a much too large slope to work with which can bring oscillations and, eventually, the controller can go "off track". If you plot the variation of the output with the duty cycle you'll get something like this:
But that's not all: because of the way the flyback works, there is a Volt*sec balance that needs to be considered, and the reflected voltage has a dependency on α exactly like the graph above; it also depends on the value of the primary inductance and the load current. The reflected voltage is the same as the output voltage at the boundary mode. Above it, it will increase, stressing the power switch. The current will also rise, causing extra losses. So it's not a practical aspect to consider.