Why the executable file type is also "DYN", not "EXEC"?

Hi all,

I find the type of executable file format on OpenBSD is "DYN", not
"EXEC":

# readelf -h /usr/bin/ldd
ELF Header:
Magic: 7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
Class: ELF64
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: DYN (Shared object file)
......

Is there any special consideration for it? Thanks very much in advance!

Best Regards
Nan Xiao