Refund after flight change to same date and itinerary as original
 

I was randomly checking date change options for a I class (Business Light) flight I booked few months ago. It shows me $10 total refund if I select same as original itinerary for 2 pax all included. I find it weird it even allows that. And it shows the change fee as 0 in the final page. If I change the date, it does show a change fee.

Since the fare code is same as original, am I missing anything by doing this change? If need to make further changes in future, it shouldn't effect right?

Probably a change in surcharges/taxes/fx.

For business light, there is a change fee. The system probably does not considers your search as a flight change and simply lists the current price minus your historical price. Apparently there is no change in the fare itself, just some forex adjustment.
I doubt that CX will actually refund you $10 if you actually try to make that change.

A while back, when HKG wasn’t quite fully out of C-19, but SIN was…CX had some cheap & very flexible (no change fee) fares exSIN, that I got a bunch of tickets on.

Went through a fair few change/reissuances with minuscule refunds on some, like the ones the OP sees. I did actually get the refunds- although the motive for the online changes was more for making the ticket ‘last longer’.

(Eventually CX wisened up, but did honour. The very last segment I flew was ~23months after the initial issuance date, with the outbound segments on that particular ticket being well after 12m after the initial issuance date..which itself was well after generic C-19 waivers were long gone)