Hello Hugues
In the question you are referring to, it is true that the subnet mask can be used for all IOS versions while the the “slash” format can be used only in some newer versions of IOS. And it is true that the DHCP command will accept any IP address within the range (not only the network address) to successfully configure DHCP. Yes, the device will accept other IP addresses, however, the most correct answer is indeed the one that uses the network address, which is 192.168.1.0 because this is how we define network address ranges for DHCP.
Even so, for clarity, the question has been adjusted to be clearer so such discrepancies will not cause problems.
As far as I know, in most new IOS, both the slash and the mask syntax are acceptable, and there is no best practice for which to use, and neither is there a deprecation of the subnet mask version of the command.
I hope this has been helpful!
Laz