Yeah you need to take into account that the LED emits in a hemisphere, so even though angles close to 0 are more intense, the circumference of the circle at that angle is small.
Luminous flux depends not only on intensity but on intensity and area, which you probably found out when reading about Lambertian distribution.
Here’s some more info:
The graph with the lobes shows that at 0 degrees there are 0 lumens emitted, because the area is 0 even though intensity is max.
Also at 90 degrees there are 0 lumens because the intensity is 0 while area is max.
You need to take the area integral of this lobe graph, not just the spatial distribution that is on LED datasheets.