These are almost certainly lady finger bananas from South East Asia. They're creamy and very sweet as far as bananas go.
I've never tried them canned but I'd say most of these would be used as an ingredient in deserts. I expect that they would indeed be packed in a sickly sweet syrup.
People have been doing hot water bath canning at home for well over a century. It works great for acidic foods like tomatoes or pickled vegetables. It’s completely safe if you follow the USDA Guide to Home Canning.
Those are not the typical cavendish-type bananas though. Those are the bluggoe (I had to look it up) or similar type of varieties that are used for cooking in Asian cuisine and desserts. When not canned, they are usually boiled when ripe and are a great sweet dessert. This canned version just makes it even sweeter with syrup.