Are you sure? We would maybe have to have someone test this.
On my M7 when I had Sprint if I had 3g and made a call it dropped day and did the call.. Which was expected.. But on 4g (LTE) it would hold the LTE data connection and use the other radio for the call.
Sent from my T-Mobile Note 3 using AC Forums.
Positive, no testing needed. It's the same on Sprints LG G2 which I own and is the same. All spark phones will have this issue due to only one transmission path. The M7 would stay connected to LTE and 1x simultaneously using 2 transmission paths, one for voice and one for data. On spark phones this apparently wasn't possible so they sacrificed the voice+data to enable spark.
Here's a very detailed article about it.
Nexus 5 and LG G2 experience temporary Sprint LTE connectivity issues due to Circuit Switched Fallback technology - Sprint 4G Rollout Updates
If you don't want to read I here's the important part:
"Sprint Triband LTE phones dropped SVLTE for eCSFB/CSFB
Up until these new Triband devices, previous Sprint LTE devices supported simultaneous voice and LTE (SVLTE). It could do so with two separate transmission paths from the antennas to the chipset. Voice/texting could run via 1xRTT on one transmission path. LTE could run a separate path, allowing data and voice to be used simultaneously.
In contrast, Sprint Triband LTE devices do not support two separate transmission paths. They have one path, shared by voice/SMS and data. We were alerted to this months in advance. However, we did not realize that the network would have to run on Circuit Switched Fallback in order for this to work and what the ramifications of this would be.
S4GRU was told by a source this past summer that Sprint and the OEM’s came to the conclusion that these new Triband LTE devices could not use SVLTE in the conventional way they used to, and it would require a lot of engineering, testing and cost to even attempt such a design change. It was decided to release Triband LTE devices without SVLTE. It may seem that the only drawback for doing that is Sprint Triband LTE devices would not be able to run simultaneous LTE data while on a phone call or when actively transmitting a text. But there is another. And it’s why many early adopters of these new Triband LTE smartphones no longer are being able to connect to Sprint LTE in many places that they used to."