This practice is WIDESPREAD.
The cause is outsourcing, and the keyword you want is either KPI or SLA.
There is a HUGE tempation to close the counters early, so they can run with the 'chit' or packing list on time - package, sardine tin, or pax - you are all the same. And if the SLA says 98% - on a plane of 300 odd, that means 6 passengers can be shafted with relative safety.
I noticed VN airport is outsourced, to a service provider. In cutting staff numbers to the bone, the counter chicks have tight and demanding schedules, with no allowance to 'finish up'. So they get revenge, by closing a tad early, so they do manage it - on average.
Any initiative, like a helper, asking if anyone in the queue 5 minutes before the flight closes - dreads the family of 14 yelling back - yeah, us. As an outsourcer, you can play or fiddle with the word close - is it refuse to serve, or refuse to serve the football team that surely will go over. If you bribe/ pay off the liason manager, the airline has buckleys of finding out.
Anyone who has outsourced, should know the importance of spot checks, and audits - sort of like computer help desk service levels, that only log problems, not fix them, and certainly not investigate down to the root cause.
And if you are a big airline, often you CANT afford to piss off the 'system', as they can cost you dearly, should they choose.
This way everybody is happy. Service provider, take a cuts, no matter how badly they deliver. Airport collects it fees and taxes, Airlines think they have a good deal - while the passengers are 're-educated' that they better arrive 2 hours early. Scheech - Imagine how bogstar chicks feel about applying 'policy'. Except intelligent passengers who know they are being diddled, and occasionally, flat out cheated - btw the outsourcing staff are cheated too - not paid for login/logout, and expected to work early and late.
So what Sg needs to do is to run a sting operation at the counter, with a few 'dummy' latecomers, to find out the real story.
In the meantime, I hope a few platinum members will write pointed letters, demanding to know, why , say QF's baggage checking lines (post electronic checkin), is 55-60 minutes long.
Be afraid. QA/Efficiency experts, who tell it as it is, don't last long, relative to the liar, who sends in a report full of 'green traffic lights'. The game sours, when HO gets letters that scream 'red light'. That is why PR consultants are overpaid - to ensure unfavorable press does not get out.
Never say Never. PS want revenge? Hand out 6 bright badges with ISO 2001 and those tick logos, 6 clipboards, 6 stopwatchs, and have gang take notes- then watch counters 'magically open'. Not quite as bad as British hospitals that employed more doctors and nurses during 'inspection rating periods'. There are statistics, statistics and dammed lies.