I'm a bit confused: does the manufacturer provide a toolchain to compile and run binary code on something that is not advertised as a SOM/SOC, but only as an lte modem?
Yes that is true in fact even the most basic modems in their line up for 2G can be used as an Application processor rather than as a plain modem.
In this case however it is more like a complete build environment that includes the Linux distribution, GCC and other relevant Linux libraries etc for the distribution.
The real FW for cellular modem is likely never exposed since that may run on a DSP core or an ASIC sub system