As for the "inline adjusters" mine just seem to be very tight to move and not do very much at all, TBH i wasn't sure that's what they was lol.
It could definitely do with a cable adjuster where the outer cable ends on the seat tube.
Yes, they are very tight, and need unscrewing for hours before having an effect on cable tension. Poor choice by Giant, given decent adjusters do actually exist.
Anyway, I've got my eye on the latest iteration of Ultegra (8000). The new front derailleur apparently has a built-in cable tension adjustment capability, eliminating the need for an inline adjuster.
I'm sure the Shimano adjusters I've bought (SM-BA01) will do a better job, with more effective and easier adjustability, than the low quality ones selected by Giant. But if necessary, an upgrade to an Ultegra 8000 front derailleur, when available, will always be an option.....