Thanks for the prompt response! So, it’s model 0461.
Indeed it must be a modified version because that specific model (0461) isn’t listed anywhere in the latest version of Anduril’s MODELS file: anduril/MODELS at trunk · ToyKeeper/anduril · GitHub
I searched further and located a PR from @loneoceans implementing that model, including the code needed for turning on the OTG/powerbank functionality in momentary mode: Added support for loneoceans Lume1 Lume X1 designs and some Anduril updates by loneoceans · Pull Request #37 · ToyKeeper/anduril · GitHub – which @Toykeeper didn’t merge and for some reason preferred to cherry-pick instead – and her cherry-picking apparently did not include the 0461 model nor the code needed for the OTG/powerbank functionality… 
@ToyKeeper: any specific reason for leaving the 0461-related code out, specially since it’s enabled by a specific #define USE_OTG_IN_MOMENTARY and bracketed by #ifdef controls, ie would be totally absent unless that #define is specifically enabled?
I need to know that because I’m planning on purchasing the X4 and OTG/powerbank functionally is vital for my use case – and to avoid the horrible behavior @m03da reported earlier (having to fully remove the head to get out of momentary mode, which needs to be activated in order to activate OTG/powerbank), I would need to modify the code.