no it specifically says has the mark of chaos ascendent, the mark of tzeentch bit is telling the reader he has a 4+ invulnerable save because its not actually written in his profile, while the other benefits are, so it deoesnt mean he actually has the mark of tzeentch as is melded with the other marks, it specifically says that in the wording
"...abaddon has melded the marks of chaos granted to him and now bears a unique mark that combines all of the gifts. because of the mark of tzeentch, the invulnerable save provided by his armor is increased to 4+. The other benefits are included in his profile"