These days SIA does not load extra meals . Because of my allergies , I cannot use BTC either but SIA does try to offer dishes which I can have . Except that some airport caterers they use , think that this means it is vegetarian or similar ..
Just a couple of examples , I often do not get butter but whatever alternative they use , and fruits instead of real desserts
The meals , mains , can be a hit & miss . So if it is something I do not care for , I skip it & the crew get really worried . But if they happen to have “ spares “ of the normal menu , they will offer to serve me from it if I can have it .

Crew meals. , it seems , are different from what is catered for passengers .