In the Portugal guidebook, in 9th edition page 209, a discussion of bus travel from Tavira to Seville, it says, “Luggage storage is not available.” Does this mean that luggage storage is not available on the bus OR does it mean luggage storage is not available in the bus station?
The long distance buses have cargo/luggage space under the buses. Sevilla might have a luggage storage place but I’m pretty certain Tavira does not.
So ... I interpret your comment to mean that the bus from Tavira to Seville DOES have space to store luggage.
I'm sure that note on p. 209 means no storage facilities at the bus and train stations (a common question). It's not related to carrying your luggage onboard the transportation itself (reliably available in the bottom of a bus or the seating area of a train).