Probably because they turn off transponders while crossing that area.

"Traffic is generally picking up in the strait, with several laden tankers seen exiting into the Gulf of Oman over the weekend, though some of them turned off their transponders. The latest was a Greek-flagged tanker carrying Iraqi crude to Singapore."

https://financialpost.com/pmn/business-pmn/iranian-crude-oil...

"Maintained by an individual developer." They state,

Maritime Intelligence — AI-powered analysis of current strait conditions, insurance markets, and diplomatic developments using real-time web data.

Energy Market Feeds — Live Brent crude oil pricing from financial data providers.

AIS Vessel Tracking — Automatic Identification System data for real-time vessel positions.

TradingView — Interactive historical oil price charts with full technical analysis capabilities.

News Aggregation — Curated news from major international outlets covering the Hormuz crisis.

though they do not say what the actual data sources are.

Try this WTO site instead. It breaks out oil, natural gas, fertilizer, and agricultural products with 7-day average and prior-year 7-day average.

https://datalab.wto.org/Strait-of-Hormuz-Trade-Tracker

Not sure I would put much faith in the stats of this clearly vibecoded slopsite