Yes it is true.
Garud Purana 2:49:13
चतुरशीतिलक्षेषु शरीरेषु शरीरिणम्॥
न मानुष॑ विनान्यत्र तत्त्वज्ञानन्तु लभयते॥ १३॥
In the eightyfour lacs of bodies of creatures one does not acquire true knowledge anywhere unless one is born as man.
Not only humans, even gods have to take birth in different yonis to attain human birth. Hence human birth is considered ...