Leaving 1 MiB free at the end of the disk space is needed for the partition table backup copy. This comes from the GPT specification. That 1 MiB space isn't left free, but it is taken by the backup copy of the partition table. GParted keeps it ut of the partition space in order to prevent corruption in case OS writes data in that partition table space.
Perhaps other partitioning programs allow to take that space too in a partition.
For MBR disks, no such space is needed as the partition table is located in the first sector of the drive, and no backup copy is kept. As I remember, there has been in the past MBR software that kept unofficial copy in the second sector but no general rule was about that.
So it isn't any bug, it is a requirement for GPT drives.
As for the initial 2048 sectors, they are the 1 MiB space needed for the MiB alignment. A drive can work with any alignment, even with the old legacy MBR scheme alignment, with a performance penalty and a faster wear out for the SSD drives. The 1 MiB has been chosen because it is multiple of the various cluster size values used by hardware manufacturers (i.e. 512 kiB, 256 kiB, 128 kiB ... ) for the newer generations of their products (SSDs and high capacity HDDs). So, since the mid 2000s the 1 MiB (2048 sector) alignment is used for new systems, GPT as well as MBR.
Of course, your partitioning can be GPT only (no MBR) due to the big size of the drive. The MBR scheme can't make partitions bigger than 2 TiB.
*** It is highly recommended to backup any important files before doing resize/move operations. ***