Has a BTC node finished all historical verification once its progress reaches 100%?

When starting a $BTC node from a snapshot, another task may still be running in the background even after the progress bar is full.

The Bitcoin Core 32.1 release notes explain that when assumeutxo is enabled—that is, when a node starts from a snapshot of the blockchain state and then verifies the historical data afterward—the node's original verification progress can return to 1.0 once it has synced from the snapshot to the latest block, and the initial block download may also show as complete. But that does not mean background historical verification has finished.

To address this, node query results now include backgroundvalidation information, which separately shows how far background processing has progressed, along with the relevant snapshot and verification progress.

If you're checking a node dashboard, first ask which task the progress bar refers to. Syncing to the latest block and completing historical verification should be checked separately; don't mark every check as complete based only on a single full progress bar. This explains what the interface means when using this snapshot feature; it is not a report of a Bitcoin network outage, and I have not checked your node.
Source: https://bitcoincore.org/en/releases/32.1/