It’s to provide for a Guildford to Farnham through service, which possibly has more demand than Ascot to Guildford. It isn’t additional in terms of numbers at Guildford, it used to be a Guildford - Ascot shuttle.
Technically it still is a Guildford to Ascot shuttle on Sundays. If it was up to me I'd run them 7 days a week but I'm going off topic here.
The turnarounds at the Farnham end are not 44 minutes as you posted above but generally 18 minutes. Realstically the turnaround at the Farnham could only come down slightly because of the need to shunt via the reception road. The Guildford to Farnham service was fitted in with basically no changes to services on other routes, it's impressive that it was managed at all in my opinion, even though the turnarounds at Guildford are probably longer than ideal. It still leaves Platform 5 and 8 for up GWR services, and 4, 5 and 8 for down GWR services though.
In terms of the trains to Gatwick, platform 5 is scheduled to be used at least once day I believe. Platform 4 is the main platform for Gatwick bound trains though. Redhill bound ones mostly use platform 8.
Could they ever resolve the issue of trains departing Guildford to Gatwick at a consistent time? Currently it's anything from x06 to x13 and that doesn't include the late night x21.
Has the requirement to run 3 tph been dropped or is it still an aspiration?
It would be great if they could some day use more trains Mondays to Saturday, so that there would be a longer turn around at Gatwick, like there is on Sundays. This would help stop trains been terminated short and started short at Redhill, which can resulting in long delays for passengers, due to the timing of other trains south of Redhill. I don't now common this currently is. I'd they had run 3tph they would have needed more trains anyway.
Whenever we have these discussions we mustn't lose site of the fact it's a secondary route of lesser importance than others. If there is ever a change in fares structure across the south east or country, I do hope this lesser importance is kept in mind too, when reviewing the prices.