bug#27884: parted reports the partition is not optimally aligned, even though it's 1MiB-aligned

Hi.

Is there any explanation to this GNU parted output?

GNU Parted 3.2
Using /dev/sde
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) unit B                                                          
(parted) p                                                               
Model: Seagate M3 Portable (scsi)
Disk /dev/sde: 4000787029504B
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:

Number  Start     End             Size            File system  Name  Flags
 1      1048576B  4000786153471B  4000785104896B  ext4

(parted) align-check                                                     
alignment type(min/opt)  [optimal]/minimal?                              
Partition number? 1                                                      
1 not aligned

Why does it say it's not aligned? Both the the start and the end are
1MB-aligned (and therefore trivially 4096B-aligned and 512B-aligned), am
I right?

In [1]: 1048576/4096
Out[1]: 256.0

In [2]: 4000785104896/4096
Out[2]: 976754176.0

For the record, at least it says it complies with "minimal" alignment:

(parted) align-check                                                     
alignment type(min/opt)  [optimal]/minimal? minimal                      
Partition number? 1                                                      
1 aligned

Regards,
Alicia.