I just found the e-mail with the eticket from the original booking.
Just above flight details in the body of the e-mail has:
You must ensure that you meet all entry requirements for your destination
As regulations may change at short notice, you should check the latest travel advisories before you fly.
And if you click that link, it takes you to the page "Vaccinated Travel Lanes (VTL)", where it has:
Transit passengers
Travellers transiting in Singapore are eligible for VTL flights if they meet the following requirements:
Be fully vaccinated against Covid-19.
Hold a valid vaccination certificate in English issued by any country.
Provide a negative result from a professionally administered Covid-19 PCR or ART test taken within 2 days prior to departure to Singapore. With effect from 23 January 2022, 2359hrs (SGT), transit travellers who have recently recovered from Covid-19 (I.e. within seven to 90 days of their last infection before departure to Singapore) may present appropriate documentary proof of their recovery instead of a negative test result. Learn more here.
Transit passengers flying from a Category IV country or arriving from Denmark, France, Germany, the Netherlands, Switzerland or the United Kingdom will be required to stay within a transit holding area, where amenities are restricted. The SilverKris Lounge will also be inaccessible due to these regulatory requirements. Learn more here.
So it is now really really important that people read all the information, every single word, at least twice, just to make sure nothing is missed. I myself had caught things I missed after reading things for the third time in preparation for my father doing this trip. Travelling post COVID is very different from travelling in 2019 B.C.