I suppose that "use this before" and "this is best if used before" would be preferable.
The compromise here is to keep printing as short as possible. I think the greater issue is that these statements don't point to any trivially available authoritative definition.
"expires on", "not safe after", or "unsafe by" are not meaningfully longer. These aren't telegrams, they're not paying a penny a character. If they're willing to mandate the phrase "best if used by," they can mandate something clear than "use by" for safety issues.
The compromise here is to keep printing as short as possible. I think the greater issue is that these statements don't point to any trivially available authoritative definition.