As for the "end of contract" bonus NOT being paid. That is certainly true in quite a number of cases. In fact there are number of cases soon to go to the Saudi Labour Court because of non payment.
It seems that good fortune may have been on the side of those who've already received their payments and in all likelyhood they're from the group who were first due to receive it because of when they are started their contracts in 2012/2013. There's no guarantee that the bonuses will be paid to those who joined 2014 and afterwards when their 3 year contracts come up for renewal.
Remember, for those that have the wisdom to see it, the government is running out of money and thus having a lot difficulty with its financing. There are are lot of government funded projects that have been stopped, because of lack of payment. KAIA is just one of them. There are also a lot of Saudi companies that rely upon government contracts that have not been paid. Their expat employees have returned home-many of them unpaid.
Work it out for yourselves. If you joined in 2012/2013 you're at the front of the que and may get your bonus. Not necessarily so if your contract started later. In those cases, I wouldn't say the bonus payment is guaranteed at all.