That is probably true, but their is no other option. 5.5V max supply voltage for the TDA1387. Battery chemistry locks you into the voltages. The LT1963 is a fast transient response regulator, and one of the best ones out there. It sounds pretty darned good. It's a matter of personal taste. The UC (and probably the LifePO4 without the regulator) are too hard for my taste.
Hardware: RPi Zero W | Allo Kali | ProtoDAC TDA1387 X8 | PGA2311 | Icepower 500ASP | Harbeth SHL5
Software: Moode 8.3.3
Source: Win 10 NAS
Software: Moode 8.3.3
Source: Win 10 NAS