That is not even remotely true. GDPR expressly affords revoking consent—and deleting any information gathered—at any time.
The point is that there may be multiple lawful bases for collecting the same personal data and it may be used for multiple purposes. The fact that consent was one of those bases does not necessarily convey a right to erasure if others still apply after consent is withdrawn.
Moreover, given that one of the other lawful bases for processing is the infamous "legitimate interest" umbrella, which could cover almost anything or almost nothing depending on subjective interpretation, the whole situation is quite ambiguous.