From the OP Reuters article:
The first two oil tankers seized were operating on the black market and providing oil to countries under sanctions, Kevin Hassett, director of the White House's National Economic Council, said in a TV interview on Sunday.
"And so I don't think that people need to be worried here in the U.S. that the prices are going to go up because of these seizures of these ships," Hassett said on CBS's "Face the Nation" program. "There's just a couple of them, and they were black market ships."
But one oil trader told Reuters that the seizures may push oil prices slightly higher when Asian trading resumes on Monday.
We might see prices increasing modestly at the opening, considering market participants could see this as an escalation with more Venezuelan barrels at risk as the tanker was not on a US sanctions list, UBS analyst Giovanni Staunovo said.
Indeed - Lloyds List, a serious shipping news source, points this out:
Centuries (IMO: 9206310), a Panama-flagged VLCC owned by a Hong Kong-registered single-ship company, Centuries Shipping Limited, was not on any sanctions list at the point that US Coast Guard personnel stopped and boarded the tanker in the early hours of Saturday morning.
...
Centuries has been flagged by Panama since March 2021 and Lloyds List could find no official notification of de-registration from Panama.
The Panama register has been contacted for clarification.
Centuries has been regularly exporting Venezuelan crude to Malaysia and China over the past year, according to Lloyds List Intelligence vessel-tracking data.
https://www.lloydslist.com/LL1155934/US-intercepts-another-oil-tanker-off-Venezuelan-coast
The thing is, the US government suddenly, and unilaterally, declaring oil exports from Venezuela (apart from their favourite Chevron) as "sanctioned" does not give them the right to seize the oil on the high seas. It just means the US should be stopping doing any business with the company they decide is breaking the sanctions.
A Bloomberg report confirms this, and also names the 3rd tanker as "Bella 1":
By Patricia Garip (Bloomberg) Another oil tanker has been boarded by the US near Venezuela, according to people with knowledge of the matter, as President Donald Trump intensifies an oil blockade on Nicolás Maduros government.
The Bella 1 tanker, a Panamanian-flagged vessel sanctioned by the US, was en route to Venezuela to load, one of the people said, asking not to be identified. The interdiction follows the boarding of the Centuries supertanker early Saturday and the Skipper on Dec. 10.
...
Saturdays boarding was notable because the ship hadnt appeared on the public US sanctions list. The Centuries tanker was flying a Panamanian flag, according to people familiar with the matter, while a Chinese company holds title to the oil.
The tanker contained sanctioned PDVSA oil, White House spokeswoman Anna Kelly said in a post on X.
https://gcaptain.com/breaking-u-s-intercepts-another-vessel-near-venezuela/