Correct. TUI is one of the few airlines that still book their slots mostly as IATA service type 'C' which to be fair is a slightly outdated scenario as they're not strictly speaking charter flights. Most regular flight series go as scheduled, service type 'J', including Jet2.
The only Jet2 flights that go in as charter are those they don't sell flight only for, such as the winter traffic they do at Gatwick on behalf of other providers. Things like Lapland flights and so on are generally service type 'C' and are more in line with the true definition of a charter flight.
https://www.oag.com/knowledge/iata-service-type-codes