Your statement is how it's ALWAYS WORKED mate in just about any airline.....
Expect to be kept busy during the Line Training with possibly no standbys and a sporadic roster working around availability of LTC's. Yes, well that's because there's no point in you being in standby, because you're useless until checked out...and frankly, until checked you're unimportant. That's true in BA, VS, CX, EK.... all airlines are the same. As a useless 200 Hour Cadet. Until line checked as proficient line FO.
Expect to fly more during the summer and less during the winter with a possibility of 2 or 3 consecutive standbys a week on occasions during winter months. So, just like Charter? Try 2 or 3 weeks of standby in a row....
If you want to complain, then fine, but
check what life's really like as a Pilot first (for those with an enquiring mind...it's sh1t). As I've already told AcePilotMurdock.