Not making partial result available during FileReader.readAsText()?

For FileReader.readAsText, the spec seems to allow partial file data being
decoded and saved in the result attribute when progress event is fired:

Make progress notifications. As the bytes from the fileBlob argument are
read, user agents SHOULD ensure that on getting, the result attribute
returns partial file data representing the number of bytes currently loaded
(as a fraction of the total) [ProgressEvents], decoded in memory according
to the encoding determination.


The partial file data read so far might not get decoded completely. Could we
choose not to decode the partial result till we retrieve all the data, just
like what FileReader.readAsDataURL does?