A block’s time stamp is valid when it's greater than the median of the last eleven blocks and less than the evaluating node’s current time plus two hours: https://bitcoin.stackexchange.com/q/915/5406

A block is allowed to have a timestamp strictly higher than the median of the last 11(?) blocks.

Timestamps are difficult in distributed systems.

It's likely timestamp miner put into block, not when block was received, can be off for hours.

Timestamping is hard

That's interesting.... from mempool's doc:

When a new block is found, mining pools send miners a block template with no transactions so they can start searching for the next block as soon as possible. They send a block template full of transactions right afterward, but a full block template is a bigger data transfer and takes slightly longer to reach miners.

In this intervening time, which is usually no more than 1-2 seconds, miners sometimes get lucky and find a new block using the empty block template.