The 1:4 ratio of the input to cascode current is not compulsory. Many text books state this as a means of maximizing gain. It is true, gain is improved due to higher output resistance.
However it is more common in my experience to decrease the ratio to a more realistic and robust level like 1:2. The reason is that in practical applications, device mismatch can exceed 25%, particularly in CMOS foundry technologies. If you use 1:4 ratio in this case, the cascode transistor can be biased at ZERO current! You've fallen off the cliff edge. In the real world of manufacturable designs, we want to stay as far away from cliff edges as possible.