Lately, I keep seeing people take the phrase "it's all written on the chain" as gospel, and I find it a bit funny.

What you see as "on-chain" in your wallet/browser is usually the result returned by an RPC node plus a view organized by an indexer, not you manually browsing through blocks.
Nodes have delays, RPCs may limit traffic or load balance to different backends, and indexers need to finish scanning, indexing, and then present a nice list for you, so the timeline you and I see for the same transaction might be different.
Even more absurd is that some services, to give you a quick "seems confirmed" status, will quietly change it once the chain is truly final.
Anyway, when I encounter "why haven't I received it" or "why hasn't it updated yet," my first reaction isn't conspiracy theory, but to check a different RPC, look up the raw transaction hash, and compare the block height.
By the way, I want to complain that recently, they've been explaining price movements by tightly linking ETF fund flows and US stock risk appetite, but on-chain data hasn't even finished syncing before they start drawing conclusions…
First, figure out which "on-chain" data source you're looking at.