A sequence of two simple patches fixes this, making the reads instant:
-- >8 --
$ time efibootmgr
BootCurrent: 0006
Timeout: 1 seconds
BootOrder: 0006,0005,0002,0003,0004
Boot0002* UEFI:CD/DVD Drive BBS(129,,0x0)
Boot0003* UEFI:Removable Device BBS(130,,0x0)
Boot0004* UEFI:Network Device BBS(131,,0x0)
Boot0005* Debian GNU/Linux trixie/sid with Linux 6.4.0-1-amd64
HD(1,GPT,2823eeb4-962f-cb4d-86ea-c0a4e460bc9c,0x800,0xfa000)/File(\KLAPKI\A2B398A10F5F4AF99258999E14093599\6.4.0-1-AMD64\VMLINUZ-6.4.0-1-AMD64)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
Boot0006* Debian GNU/Linux trixie/sid with Linux 6.4.0-1-amd64
HD(1,GPT,2823eeb4-962f-cb4d-86ea-c0a4e460bc9c,0x800,0xfa000)/File(\KLAPKI\A2B398A10F5F4AF99258999E14093599\6.4.0-1-AMD64\VMLINUZ-6.4.0-1-AMD64)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
real 0m0.002s
user 0m0.001s
sys 0m0.000s
-- >8 --
(some would say this is a .168/.002=84x speed improvement).
And bumps the actual max read rate by 50%:
-- >8 --
fcntl(4, F_SETFD, FD_CLOEXEC) = 0
getdents64(4, 0x55cd1adb8420 /* 104 entries */, 32768) = 7568
getdents64(4, 0x55cd1adb8420 /* 0 entries */, 32768) = 0
close(4) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0002-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\7\0\0\0\1\0\0\0\r\0U\0E\0F\0I\0:\0C\0D\0/\0D\0V\0D\0"..., 4096) = 59
read(4, "", 4037) = 0
close(4) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0003-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\7\0\0\0\1\0\0\0\r\0U\0E\0F\0I\0:\0R\0e\0m\0o\0v\0a\0"..., 4096) = 67
read(4, "", 4029) = 0
close(4) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0004-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\7\0\0\0\1\0\0\0\r\0U\0E\0F\0I\0:\0N\0e\0t\0w\0o\0r\0"..., 4096) = 63
read(4, "", 4033) = 0
close(4) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0005-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\7\0\0\0\7\0\0\0\314\0D\0e\0b\0i\0a\0n\0 \0G\0N\0U\0/\0"..., 4096) = 610
read(4, "", 3486) = 0
close(4) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Boot0006-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\7\0\0\0\7\0\0\0\314\0D\0e\0b\0i\0a\0n\0 \0G\0N\0U\0/\0"..., 4096) = 610
read(4, "", 3486) = 0
close(4) = 0
openat(AT_FDCWD, "/sys/firmware/efi/efivars/BootNext-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/sys/firmware/efi/efivars/BootCurrent-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\6\0\0\0\6\0", 4096) = 6
read(4, "", 4090) = 0
close(4) = 0
newfstatat(1, "", {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x2), ...}, AT_EMPTY_PATH) = 0
write(1, "BootCurrent: 0006\n", 18BootCurrent: 0006
) = 18
openat(AT_FDCWD, "/sys/firmware/efi/efivars/Timeout-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\7\0\0\0\1\0", 4096) = 6
read(4, "", 4090) = 0
close(4) = 0
write(1, "Timeout: 1 seconds\n", 19Timeout: 1 seconds
) = 19
openat(AT_FDCWD, "/sys/firmware/efi/efivars/BootOrder-8be4df61-93ca-11d2-aa0d-00e098032b8c", O_RDONLY) = 4
read(4, "\7\0\0\0\6\0\5\0\2\0\3\0\4\0", 4096) = 14
read(4, "", 4082) = 0
close(4) = 0
-- >8 --
Patches attached, tested against 38-2.