Seriously is this because of discrimination or due to some sort of "optimization" that is not explained in the article. Vendors speaking same language kinda thing perhaps.
Cant they make people do their Hajj in waves?
Regarding doing it in waves. Its technically not possible because its a certain time of the year that one can do Hajj, and its not a whole year thing otherwise it wouldn't be such a issue. Its a five day period starting on a specific date determined by the Islamic Calendar which is based on the Lunar Cycle.
So, For Example, the Hajj start this year on the 12th of this month and continues for a five day period in which millions of people will flock to the country. Last year it was 2,000,000 people in total.
At the end of day, it is possible to manage large crowds such as this but Saudi's are basically not putting in the effort. The amount of resources they have, don't justify this being this bad. Hell, Most other Islamic countries also often criticize Saudi's specifically on this issue. I think Iran has called them murderers or something for last years accident.
Problem is that there's a fairly strict clock synchronizing the motions of all pilgrims.