Why do these 10GBASE-LR optics work over OM3 fibre?

(Someone else installed this, I don't know why it works.)

Dell S4810 switches (essentially 48 SFP+ ports) with 10GBASE-LR optics is working over OM3 multi-mode fibre. I don't understand how that works, because those optics are for single-mode fibre.

Optics are https://www.serversupply.com/NETWORKING/TRANSCEIVER/10%20GIGABIT/DELL/FTLX1471D3BCL-FC.htm based on the product code written on them.

Fibre run is approximately 100 metres in length. Traffic is fairly low but there are no reported issues.

#show interfaces te0/46 TenGigabitEthernet 0/46 is up, line protocol is up Port is part of Port-channel 1 Description: BDI-Sw1-46 Hardware is DellEth, address is 00:01:e8:d8:6d:ab Current address is 00:01:e8:d8:6d:ab Pluggable media present, SFP+ type is 10GBASE-LR Medium is MultiRate, Wavelength is 1310nm SFP+ receive power reading is -4.4843dBm Interface index is 1054468 Internet address is not set Mode of IPv4 Address Assignment : NONE DHCP Client-ID :0001e8d86dab MTU 9216 bytes, IP MTU 9198 bytes LineSpeed 10000 Mbit Flowcontrol rx on tx on ARP type: ARPA, ARP Timeout 04:00:00 Last clearing of "show interface" counters 177w4d20h Queueing strategy: fifo Input Statistics: 448290370538 packets, 296603021447113 bytes 12251479261 64-byte pkts, 239694702364 over 64-byte pkts, 2931193476 over 127-byte pkts 2184533491 over 255-byte pkts, 17062243115 over 511-byte pkts, 174166218831 over 1023-byte pkts 12298332518 Multicasts, 53046458 Broadcasts, 435938991562 Unicasts 0 runts, 0 giants, 12192104807 throttles 0 CRC, 0 overrun, 0 discarded Output Statistics: 575498521760 packets, 683039443152224 bytes, 0 underruns 3296437949 64-byte pkts, 108159071822 over 64-byte pkts, 2708592810 over 127-byte pkts 2088690217 over 255-byte pkts, 37762795859 over 511-byte pkts, 424740580282 over 1023-byte pkts 106209030 Multicasts, 30561692 Broadcasts, 575361751038 Unicasts 3257647179 throttles, 0 discarded, 0 collisions, 0 wreddrops Rate info (interval 299 seconds): Input 00.00 Mbits/sec, 113 packets/sec, 0.00% of line-rate Output 00.00 Mbits/sec, 93 packets/sec, 0.00% of line-rate Time since last interface status change: 16w0d5h 

I'm using other pairs on this OM3 fibre with Cisco 10GBASE-SR optics, which is the type I'd expect to need to use on this type of fibre.

Why does it work?