This is not 100% true but it has some truth to it.
To understand the Quran, you have to understand it through the Sunnah of the Prophet salla Allahu alaihi wa salaam and the our righteous predecessors.
This can be only done perfectly trough knowing the hadeeth and having the necessary tools that enable a person from distinguishing an authentic hadeeth from a fabricated one.
But a person is also in need to know the Arabic language to be able to understand the Quran as it was revealed in Arabic.
Therefore, it is a collective of sciences and not only one.