Yes basically it is that. I've often heard that the initial plus booster can be enough to cover them for life. The Panleuk part is actually only recommended by the makers to be done every 3 years - its not required yearly as it lasts anything upto 7 years so they average it out.
I think cat flu is recommended yearly because of the different strains but again I don't even think its effective
I had (my mom has her now) a Persian who was fully vaccinated and when she was 2 I got a rescue cat - bearing in mind she is 16 now so going back a long time. The rescue were not honest with me and said the kitten was 'cured' of cat flu - which of course can not happen.
When she arrived at ours she started to shed the virus due to stress of a new environment and my Persian contracted it.
....I think alot of vets vaccinate as standard every year whether its suggested by manufacturers or not and many will repeat the entire course even if the cat is only a bit late.