The /32 is going to matter for the addresses outside the /48. The customer only wants one /48 to go through Cloudflare; from the article context, probably because that /48 is under DDoS. DDoS scrubbing services are expensive in dollars and latency (and sometimes network features), so you only want to expose your traffic to that when necessary. When the DDoS is over, you don't want any of your traffic going through Cloudflare, so you withdraw the /48, you wouldn't want to advertise the /32 through Cloudflare at that point either.

Using the article's example ranges:

If the customer's IP 2001:db8::1 is being DDoSed, then they advertise 2001:db8::/48 through cloudflare, but 2001:db8:1::1 doesn't want that; it'll be handled by their 2001:db8::/32 announcement on their usual ISP(s)