tunnel-ipv4-source maps to nw_src instead of tun_src while writing flow onto OVS

While trying to write a flow on OVS from ODL with the body shown below. The flow is added successfully but the field "tunnel-ipv4-source" got mapped to "nw_src" in OVS instead of "tun_src".

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<flow xmlns="urn:opendaylight:flow:inventory">
<hard-timeout>0</hard-timeout>
<idle-timeout>0</idle-timeout>
<priority>150</priority>
<flow-name>flow1</flow-name>
<match>
<ethernet-match>
<ethernet-type>
<type>2048</type>
</ethernet-type>
</ethernet-match>
<tunnel-ipv4-source>10.2.1.1/32</tunnel-ipv4-source>
<tunnel>
<tunnel-id>5555</tunnel-id>
</tunnel>
</match>
<id>1</id>
<table_id>0</table_id>
<instructions>
<instruction>
<order>0</order>
<apply-actions>
<action>
<output-action>
<output-node-connector>1</output-node-connector>
</output-action>
<order>0</order>
</action>
</apply-actions>
</instruction>
</instructions>
</flow>

Response from OVS dump-flows for the above flow is shown below :

cookie=0x0, duration=3.237s, table=0, n_packets=0, n_bytes=0, idle_age=3, priority=150, ip,tun_id=0x15b3,nw_src=10.2.1.1 actions=output:1

Why tun_src does not appear on OVS flow, instead it gets mapped to nw_src?

Whereas when the flow is added using ovs-ofctl add flows cmd, the parameter tun_src getting correctly mapped.

cookie=0x0, duration=3.237s, table=0, n_packets=0, n_bytes=0, idle_age=3, priority=150, tun_id=0x15b3, tun_src=10.2.1.1 actions=output:1