PinkPony

You said it yourself.
 
You are heading into the wind in order to follow the LNAV track. 
 
Boeing offers two ND orientations as customer options on all their glass cockpit aircraft. HDG up, which is what you currently have set and TRK up. You can change this via the operations center for a specific repaint, or in the FMC via the AIRCRAFT ---> DISPLAYS menu. 
 
In order to make life simple for operators who chose HDG up orientation, Boeing added a very handy white line that begins at the aircraft symbol (the triangle). This white line represents your track, which is why the aircraft will align that line with the LNAV track when in LNAV mode. HDG will only match TRK in a zero wind or perfect tailwind/headwind scenario.
 
On the other hand, if you set the orientation to to TRK up (Boeing default option) your track will always appear vertical on the ND, as the ND is orientated in TRK mode.
 
Emirates, KLM, Lufthansa, British Airways are some real world operators who purchased the HDG up option for the ND.
 
Cathay Pacific, United Airlines are some of the operators who selected the TRK up option on the ND.
 
I suggest you refer to the FCOM, as it will give you a description of both options and provide further clarity!
 

Correct regarding tailskid and clock.
 
The WXR is simply one of the many customer options offered on the B777 (nowhere near as many as on the B744). BA in this case chose the more expensive and hence less popular Honeywell RDR-4000. As did Cathay, Air Canada etc. ultimately these decisions are made by various people such as hhief Pilots, Technical pilots, bean counters (of course).
 
Technically speaking the RDR-4000 is a pretty incredible and highly automated WX radar. I know a B737 pilot whose airline just switched from the WXR-2100 to the RDR-4000 and his experience has been very positive.
 
On the other hand, Turkish chose to switch to from the RDR-400 to the WXR-2100 on their most recent batch of B77Ws!