[brigade]

The profiles only matter if you want to be decodable by hardware decoders. If you only care about software decoders, which must be true if JPEG-XL is your comparison, then you don't have to use the HEIF grid for large dimensions, and the better question is how much memory your application will allow to be allocated. Because chances are JPEG's maximum 65535x65535 exceeds it that too.

AV1 itself allows a maximum of 65536x65536 for a single picture, whereas the HEIF grid hypothetically allows even more than that regardless of how large each individual picture is (HEIF grid dimensions are 32-bits). As a practical example, libavif will not use the grid for large dimensions unless explicitly told to do so, by default producing files that aren't compliant to either baseline or advanced profiles.

(to further my pedantry against your source: AVIF is a subset of HEIF; what people usually mean by "HEIF" is the HEIC subset)