I have a serious issue with the NWT's insertion of "Jehovah" in the NT when there isn't a single Greek NT manuscripts containing the name of God. The insertion of "Jehovah" into the NT of the NWT has corrupted some NT texts. Romans 14:8 is a notable example of this, where the NWT erroneously renders "kyrios" (Lord) as "Jehovah" even though the very next verse (Romans 14:9) makes it clear that the "kyrios" of Romans 14:8 refers to Jesus and not Jehovah.
However, even though I don't agree with the NWT replacing "kyrios" with "Jehovah" at Romans 10:13, the fact is that that particular "kyrios" does in fact refer to "Jehovah" (YHWH). I say this because Romans 10:13 is quoting an OT text - Joel 2:32 - that uses YHWH. It might be tempting, from a Trinitarian standpoint, to use Romans 10:13 to suggest that Jesus is Jehovah given that Romans 10:9-11 speak about the importance of faith in Jesus.
But Romans 10:13 is only being used to bolster a point made in Romans 10:12 and the point being made at Romans 10:12 is the impartiality of God. Romans 10:13 was quoted by the writer as an OT example of God's impartiality because it says EVERYONE who calls on God's name will be saved. It's simply not an attempt on the part of the writer to suggest that YHWH of the OT is the same Jesus of the NT.
Having said that, it is also possible that the writer of Romans 10:13 considers calling on the name of Jesus to be tantamount to calling on the name of Jehovah and therefore in fulfillment of Joel 2:32 - all without intending to suggest that Jehovah is Jesus. How so? Think about it: Jesus means "YHWH is salvation" and Joel 2:32 says people will be saved by calling on the name of YHWH. The name Jesus embodies in one word the message of Joel 2:32. Jesus is YHWH's provision for salvation. By calling on the name Jesus in faith, one is putting faith in YHWH's provision of salvation and is therefore putting faith in YHWH. He is quite literally saying: "YHWH is salvation". So calling on the name of Jesus is really calling on the name of Jehovah by proxy, as it were. So it is very possible and very reasonable for the writer to apply Joel 2:32 to calling on the name of Jesus in faith without believing or intending to suggest that Jesus is Jehovah.