That's a good point you make, but I think it's not quite so clear cut as you say. I'm not sure as a matter of contractual construction, that the warranty exclusion expresses intended purpose, nor that it successfully avoids SOGA liability. Even if it does (which I'm not sure) demonstrate intent to adopt a given level of risk and no more, firstly (and in your favour) it seems to just relate to the intent to limit the extent of the gratuitous promise of the warranty - especially given the red hand rule (which requires that onerous clauses be made prominent in order to be incorporated into contracts - and an onerous clause which is implied rather than written is even less prominent). I think you're imferring or imputing intent, rather than actually seeing it in the flesh. However alternatively, if it did also relate to intent regarding SOGA, it would amount to a non-negotiated clause attempting to reduce or exclude liability for breach of what would otherwise be those SOGA obligations.
That would make it assessable for fairness under s 18 UCTA 1977 and s 5 UTCCR 1999.
Given they haven't attempted to explicitly limit SOGA liability, and even if they had that would be assessable for fairness, the real question I think is what's fair in all the circumstances, and this may come down to reasonable durability, and that in turn may turn on the design and its appropriateness for being used as an ebike - and perhaps how much you used it too.
Can you post a link to the type of bike it was?