I partially disagree with this argument. Since Bitcoin preserve backward compatibility, that means people need to move their coin to address which use better cryptography. There's also consideration new technology (such as SegWit and Taproot) took many years before it's activated on Bitcoin network. Although for now, there are definitely other higher priority than choose and implement QC-resistant cryptography.
We do not know the capabilities of quantum computers or what may happen in the future, but Bitcoin has the ability to keep pace with variables and is not a rigid technology in a specific thing.
Old addresses (Which was not sent from) can be considered safe, even if quantum computers has developed. Therefore, if you buy Bitcoin, move it to a new address and don't reuse address, then you are safe.