For practice, I just planned and simulated a route from Kemble (EGBP) to Turweston (EGBT).  I planned the route to the north of Banbury so as to be able to position for an overhead join to either runway (all circuits at Turweston being to the north).  However, before reaching Banbury I crossed the extended centreline of Rwy 09 (which, as it happens, with today's weather would have been the landing runway - but I was 15 nm out!) and SD flipped into virtual ILS mode.  Whilst the simulator continued to fly the planned route (exactly as I would have done!)  All the HSI information plus distance to go, time to go etc were now changed to reflect the 'ILS' 09.  I could find no way of reverting the display to Nav, nor any reference to this in the manual.

Surely crossing an extended centreline at your destination without intending to make an immediate approach isn't an uncommon phenomenon, so I can't believe that it's not possible to tell SD that a straight-in from that distance out is not one's intention?  I assume that I've missed something?

Gadget

(SkyDemon for Android v 3.5.0.19917 running on Samsung Galaxy Tab 3 8") 

If you are in the extended centreline and flying towards the threshold, SkyDemon assumes you are on final approach and some of the instruments change to show you timings to the threshold. While in that mode the PLOG can easily be opened to show you timings to other intermediate waypoints if you have them. If you're flying down an extended centreline it is in most cases unlikely you intend to subsequently break off and join a circuit.

However if you do subsequently alter course to enter a circuit, SkyDemon will no longer assume you are on final approach and the timing/distance instruments will revert. However at this point in your route (entering a circuit) the timing/distance instruments are not very useful anyway, because they are relating to the airfield ARP and SkyDemon does not know your precise intentions regarding the circuit.

This is not related to the OP which concerned whether SkyDemon will assume you're on final approach if you are simply flying across (not down) the extended centreline for somewhere.

All of this is assuming that you haven't explicitly told SkyDemon your intentions (i.e. landing runway and circuit direction). If you have done so, SkyDemon will not implicitly select a runway.