That's not correct, the 30 items is a reporting threshold.
The £1,000 is a Trading Allowance for small business sellers. If a business seller has sales over £1,000 they need to complete a tax return.
A private seller may have sales over £1,000 and is not required to complete a tax return. They would be listing their own personal bits and pieces such as items from their wardrobe, loft, garage etc.
eBay will be reporting sales of over 30 items or £1,740 (figure may change due to inflation, it's 2000 Euros).
This eBay guidance page explains what's being reported and when:
https://www.ebay.co.uk/help/account/regulatory/uk-digital-sales-reporting?id=5454&st=3&pos=1&query=U...