It’s a known issue and nothing to worry about. The difference between local Lighthouse runs and those from PageSpeed insights comes from the fact that the latter is not supporting HTTP/2. Vue Storefront highly relies on code-splitting and prefetching which is a standard type of optimization for HTTP/2 but something that can lower the score on HTTP/1 because of it’s parallel connections limit. TTI metric seems to be affected the most.
Thankfully it’s something that Chrome team is working on and should fix soon - https://github.com/GoogleChrome/lighthouse/issues/7326
For now i recommend using local Lighthouse runs to measure the performance.