The hours can then be made up via ICUS to achieve the ATPL command requirements.
The steady dumbing down of the minimum command hours required before qualifying for an Australian ATPL has been going that way for years.
Now I stand to be corrected, but originally you had to have among other things, a minimum of 500 hours real command time to qualify for an ATPL. It could even be all on singles. I believe it was the original Qantas cadet system that started the lowering of that standard. That was when it was realised that after 10-15 years of F/O time on Super Connies, DC4's and 707's, it was discovered that when pilots finally attained the company seniority to begin command training, they had nowhere near 500 hours of command time. In fact some still only had the basic CPL command time of 100 hours. To allow co pilots to obtain command time (or was that the first use of ICUS especially designed for Qantas former cadets) Qantas had a Dc3 and an HS 125.
Similarly Qantas in the 1960's or early 1970's (?) arranged with small regionals including Solair in the Solomon Islands, to take the Qantas 200 hour cadets and give them work flying light singles to eventually reach 500 command hours. C206, C185's Queen Air and Aztecs come to mind. Nevertheless, it was valuable command experience.
Qantas leaned on the then DCA to lower the ATPL min command hours (500) requirements. Being the national carrier flying the Red Kangaroo, Qantas had great influence on DCA and in those days if Qantas said Jump - DCA officials usually jumped. . Eventually, DCA caved in and now the ATPL is not worth a pinch of salt as a measure of experience since the minimum qualification has been watered down to present day requirements of 75-100 real command hours. The rest was made up with useless ICUS.
Many consider ICUS a con and also not worth a pinch of salt as it is not real decision making time but simply a continuation of basic co-pilot time using weasel words.