not always true. The halving last week didn't push the price up.
The halving of block reward shouldn't push the price up.
I don't know who ever came up with that concept in the first place? I have seen this incorrect statement on several altcoin threads.
On a per-time-basis only half the amount of coins are being added to the market compared to before the block-halving, so one could think this has an effect on price. However there are of course a lot of other influences to factor in..