Not many of Conte's wingbacks have great delivery. Peresic probably has the best delivery into the box that he has worked with from Chelsea on wards and wouldn't describe it as great.Salah was apparently second choice at Liverpool, as was Kulsevski for us, and Son. Shit happens.
I will say though that I don't think he's a "conte wingback" like people are saying. A Conte WB has to have either great delivery into the box (trippier) or really good at scoring (doherty). Spence's supposed traits don't fit that mould.
Wingbacks in Conte's system tend to run/dribble to the byline and play cut backs, rather than crossing (Spence is good at this).