Expresscard AHCI Controller not Detected at Hotplug

Apologies if I've chosen the wrong mailing list to start with. I'm not certain where this hickup is happening, so I'm not sure who to talk to.

I have a laptop (Lenovo w510) with an Expresscard/34 slot. If I hotplug my multi-i/o card, it works fine (well, it's detected and is enumerated):

acpiphp_glue: _handle_hotplug_event_bridge: Bus check notify on \_SB_.PCI0.EXP4
acpiphp_glue: _handle_hotplug_event_bridge: re-enumerating slots under \_SB_.PCI0.EXP4 pci 0000:05:00.0: [9710:9912] type 0 class 0x000700
pci 0000:05:00.0: reg 10: [io 0x0000-0x0007]
pci 0000:05:00.0: reg 14: [mem 0x00000000-0x00000fff]
pci 0000:05:00.0: reg 24: [mem 0x00000000-0x00000fff]
pci 0000:05:00.0: PME# supported from D3hot D3cold
pci 0000:05:00.1: [9710:9912] type 0 class 0x000700
pci 0000:05:00.1: reg 10: [io 0x0000-0x0007]
pci 0000:05:00.1: reg 14: [mem 0x00000000-0x00000fff]
pci 0000:05:00.1: reg 24: [mem 0x00000000-0x00000fff]
pci 0000:05:00.1: PME# supported from D3hot D3cold
pci 0000:05:00.2: [9710:9912] type 0 class 0x000701
pci 0000:05:00.2: reg 10: [io 0x0000-0x0007]
pci 0000:05:00.2: reg 14: [io 0x0000-0x0007]
pci 0000:05:00.2: reg 18: [mem 0x00000000-0x00000fff]
pci 0000:05:00.2: reg 24: [mem 0x00000000-0x00000fff]
pci 0000:05:00.2: PME# supported from D3hot D3cold
pci 0000:05:00.0: BAR 1: assigned [mem 0xf0000000-0xf0000fff]
pci 0000:05:00.0: BAR 5: assigned [mem 0xf0001000-0xf0001fff]
pci 0000:05:00.1: BAR 1: assigned [mem 0xf0002000-0xf0002fff]
pci 0000:05:00.1: BAR 5: assigned [mem 0xf0003000-0xf0003fff]
pci 0000:05:00.2: BAR 2: assigned [mem 0xf0004000-0xf0004fff]
pci 0000:05:00.2: BAR 5: assigned [mem 0xf0005000-0xf0005fff]

 pci 0000:05:00.0: BAR 0: assigned [io  0x3000-0x3007]
 pci 0000:05:00.1: BAR 0: assigned [io  0x3008-0x300f]
 pci 0000:05:00.2: BAR 0: assigned [io  0x3010-0x3017]
 pci 0000:05:00.2: BAR 1: assigned [io  0x3018-0x301f]

pci 0000:05:00.0: no hotplug settings from platform
pci 0000:05:00.1: no hotplug settings from platform
pci 0000:05:00.2: no hotplug settings from platform
acpiphp_glue: acpiphp_check_bridge: 1 enabled, 0 disabled
Serial: 8250/16550 driver, 0 ports, IRQ sharing enabled
serial 0000:05:00.0: enabling device (0000 -> 0003)
Couldn't register serial port 0000:05:00.0: -28
serial 0000:05:00.1: enabling device (0000 -> 0003)
Couldn't register serial port 0000:05:00.1: -28
parport_serial 0000:05:00.2: enabling device (0000 -> 0003)
parport0: PC-style at 0x3010 (0x3018), irq 17, using FIFO [PCSPP,TRISTATE,COMPAT,ECP]

If I eject my multi-i/o card and hotplug my esata card (Marvell 91xx based), nothing is seen:

acpiphp_glue: _handle_hotplug_event_bridge: Bus check notify on \_SB_.PCI0.EXP4
acpiphp_glue: _handle_hotplug_event_bridge: re-enumerating slots under \_SB_.PCI0.EXP4
acpiphp_glue: acpiphp_check_bridge: 0 enabled, 1 disabled
acpiphp_glue: _handle_hotplug_event_bridge: Bus check notify on \_SB_.PCI0.EXP4
acpiphp_glue: _handle_hotplug_event_bridge: re-enumerating slots under \_SB_.PCI0.EXP4
acpiphp_glue: acpiphp_check_bridge: 0 enabled, 0 disabled

If I do:

echo 1 > /sys/bus/pci/rescan

pci 0000:05:00.0: [1b4b:9123] type 0 class 0x000106

 pci 0000:05:00.0: reg 10: [io  0x8000-0x8007]
 pci 0000:05:00.0: reg 14: [io  0x8040-0x8043]
 pci 0000:05:00.0: reg 18: [io  0x8100-0x8107]
 pci 0000:05:00.0: reg 1c: [io  0x8140-0x8143]
 pci 0000:05:00.0: reg 20: [io  0x800000-0x80000f]
 pci 0000:05:00.0: reg 24: [mem 0x00900000-0x009007ff]
 pci 0000:05:00.0: reg 30: [mem 0xd0000000-0xd000ffff pref]
 pci 0000:05:00.0: PME# supported from D3hot
 pci 0000:05:00.0: BAR 6: assigned [mem 0xf2800000-0xf280ffff pref]
 pci 0000:05:00.0: BAR 5: assigned [mem 0xf0000000-0xf00007ff]
 pci 0000:05:00.0: BAR 4: assigned [io  0x3020-0x302f]
 pci 0000:05:00.0: BAR 0: assigned [io  0x3000-0x3007]
 pci 0000:05:00.0: BAR 2: assigned [io  0x3030-0x3037]
 pci 0000:05:00.0: BAR 1: assigned [io  0x3038-0x303b]
 pci 0000:05:00.0: BAR 3: assigned [io  0x303c-0x303f]

ahci 0000:05:00.0: irq 46 for MSI/MSI-X
ahci 0000:05:00.0: controller can do FBS, turning on CAP_FBS ahci 0000:05:00.0: AHCI 0001.0200 32 slots 8 ports 6 Gbps 0xff impl SATA mode ahci 0000:05:00.0: flags: 64bit ncq fbs pio
scsi28 : ahci
<snip x26>
scsi 35:0:0:0: Processor Marvell 91xx Config 1.01 PQ: 0 ANSI: 5
scsi 35:0:0:0: Attached scsi generic sg5 type 3

It's detected and works fine.

Is this a PCI bug, an ACPI bug, a hardware issue, or working as designed? Is there a 'better' way I should be handling this use case?