Paradoxically, pruning and validating only the current blocks may be sufficient for security, but only if it doesn't become too common.

It is better not to provoke the evolution of the protocol towards increasing scalability, which would not only threaten decentralization, but also security.
There can always be a bug that validators cannot detect and that will not be disclosed until a full chain audit by inquisitive, independent researchers.
As was the case with the Stellar coin once
https://coinmetrics.substack.com/p/coin-metrics-state-of-the-network-37f