You got me curious enough now to check out your Sony BDP-BX110's specs and here's the link in case you have not been there yet.
https://docs.sony.com/release/SPECS/BDPBX110_mksp.pdf
So it is true that this, and likely the other newer models, has limitation decoding DTHD. I agree it is weird that it could decode DTSHDMA. The HDMI out can still handle all lossless/uncompressed signal including LPCM. That means if you have a disc that has LPCM7.1 the BX110 can output it.
As to why they could not decode Dolby TrueHD, you have to ask Sony. I also checked the price of the older models such as the BX38,39,590 and they all seem to start at $199.99.
The bottom line is, even if you have the older model, such as my PS3, BX38, BX59, you will still have the same issue because your SR5001 is the show stopper as it can't handle 48 kHz in multchannel and will mute 96 kHz. You've got to trust what the manuals tell you, most of the time anyway. Sorry I did not read the Specs of the BX110 in the first place, but what a surprise though..