Hi Ben, flap ye not.
If by .gpx you mean the book's routes – now all updated with edition 3 – then the key waypoints are all you need to get going alongside the book's description. Once on a trail, Olaf (or similar) are highly recommended as they provide a tracklog (continuous line) to follow, aided by Tim's detailed pictorial descriptions (if you can match up the routes).
But most of the time you will simply rely your eyeballs and other senses to keep on track. Imo, people get too fixated on gpx and tracklogs, but if you're going somewhere new and have little nav background, aome apprehension is understandable.
Olaf + key waypoints are just a helpful reassurance. Once you get in the swing of things you'll need them less and less, and within a couple of trips the same goes for the guidebook too.

A 64S is rather a small-screened unit, even if it is colour. Until I bought an expensive Montana I used cheap, used 5-inch Nuvi satnavs from 50 quid alongside my GPS60. Its easier to read but a bit fragile under a hammering and iirc you have to zoom right in to before secondary Olaf routes become visible. It took me years before I realised that, but I still managed to do what I did.

Depending on where you go and what you do, I think it may be the heat which holds you back, rather than insufficient GPS data. If it ever doesn't feel good for whatever reason, just turn back. Riding alone, I did that a couple of times last March. Too much GPS can lead you into trouble, if you disregard other factors.

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Morocco Overland 4 (2025) • Trans Morocco Trail