Here I want to share my experience with the use of log preservative. Over 6 years, the UV rays on the sunny side of the facade have "aged" it severely. Compare photos of the sunny and shady sides of the house.
Do not believe the promises that everything will stand for centuries. Nothing lasts forever, be prepared to paint the facade every 6 years. Who's had this kind of experience?
Who told you that the preservative protects against ultraviolet light? A preservative is only supposed to do one thing: prevent infestation on the wood. If the material is tinted, that doesn't mean the tint is durable.
Your material doesn't look like antiseptic because it has a film/coat effect on the north side, and you can no longer see it on the south side (abrasion of the layer has occurred).
This is most likely called "covering antiseptic", which is the very product of the marketers. It is a kind of varnish with fungicidal properties.
Color: The more saturated the color, the more likely it is to fade.
Abrasion: The coating will abrade under load.
Impregnation (oil, primer, antiseptic, etc.) – absorbed into the substrate (in this case wood).
Coating composition (varnish, paint, varnish, enamel) – film-forming composition.
Different tasks, the first have an impact on the substrate, the second – to protect it.
To combine and do "all in one" is technically very difficult.