Searching for SQ Saver Upgrades

[PlutekPlutek]

Hi,
I am booked on SQ237 on 2 February in Economy (Y).
I want to upgrade to Business, and I have the points in my VA account. Don't want to transfer unless I am sure to get the seats.
When I search for reward flights, I can see on that day, on that flight, that there is reward seats available, without a waitlist. See screenshot.

I was about to transfer the equivalent of 45000 miles required for a Saver upgrade, but thought I'd call the centre and double check. The agent is saying that only Standard seats are available.
Is there another way to search if there are upgrade'able seats available - do they come from different buckets than these reward seats ?
Clearly a saver reward seat is available, so I'm not sure why the agent is saying only Standard is available. Any ideas ? Should I try calling and speaking with another agent ?

Cheers
L

 

[cove]

Go SQ217 in Suites for 63,750 on line.
It is the A380 so try for Krug and Dom Perignon then Vodka with the caviar and finish with a fine red.
Go to the best seeing it is less Kris Miles.

 

[PlutekPlutek]

Can't change the flight. I arrive in SIN from ICN @~22:00. I need to connect back to NTL, so would need an extra night in SIN, and then an extra night in MEL. SQ237 is the only one that works.
Also SQ217 is a daytime flight, whereas SQ237 is a redeye. I can handle a daytime flight in Y - but its nice to have a bed for a redeye.

 

[PlutekPlutek]

I rang them for a second time, and the second agent said that the waitlist is not available (not showing) on that flight because its full. There is apparently only one seat in Standard.
Considering using Standard and forking out the extra points, but want to be 110% sure the Saver is really not available.