VLAN access port question

I saw this in a customer's environment and I'm not sure how its working?  Doesn't SW1 need to be on the same VLAN as the CUSTOMER?  

SW3 G1/1/1 (CUSTOMER) ---------   SW1 F1/0/33(vendor fiber backbone network)  -------- SW2 G1/1/1 (CUSTOMER)

SW1
interface FastEthernet1/0/33
switchport access vlan 223
switchport mode access
end

SW2
interface G1/1/1
switchport access vlan 507
switchport mode access
end

SW2
interface G1/1/1
switchport access vlan 507
switchport mode access
end