First off, that was TSMC that sent its workers back to work, and TSMC doesn't do DRAM.
Second off, just because the machinery was undamaged, it doesn't mean a batch didn't get ruined from an unexpected interruption.
But yes, the earthquake offers plausible deniability to increase prices.
It can be a bit more complex than that. I.e. company A gets supplied from companies B and C, of which company B has a landslide between them and the port, and company C needs to recalibrate a production line.
In any case, when a company has an annual revenue of $70bn from production there, that comes down to about $8 million per hour. And production being halted for 10 hours, $80 million right there "lost".
Add to this, that in Hualien Port as of yesterday, out of 26 terminals, 18 were not operating. This port in particular has seen some damages, such as ground cracking and sinking, including impact on buildings, where the repairs do not have the same priority as rescuing people trapped in tunnels.
And this port last year handled nearly 8.83 million tonnes of cargo (and thousands of cruise passengers). This may now mean, that a lot of the cargo gets redirected to other ports, which in turn may face some logistical challenges due to that.
And all that may quickly mean, that a single company runs hundreds of millions of $ short of what they meant to have this year (and already planned for to spend), with additional expenses, such as due to logistics.