The businesses who use that question are interpreting the law in a BS manner.
The applicability of the Switchblade Act, re: Armed Forces personnel and LEOs, reads (nutshell version), you have to be the procurement officer (the person who buys stuff in large quantities) or a supply officer (the person who redistributes what the procurement officer bought) for a Armed Forces or law enforcement organization in order to SHIP switchblades across state lines and not have to pay a fine or go to jail. Nothing about "be in the military to buy". Nothing about "be a LEO to buy".
Here's the text of the law -
https://www.gpo.gov/fdsys/pkg/STATUTE-72/pdf/STATUTE-72-Pg562.pdf
What the businesses are doing is misinterpreting or "creatively interpreting" what "Section 4, paragraph 3", which prescribes the Armed Forces exceptions to the law, actually says.
Breaking 4-3 down in computer code logic -- it says -
IF an Armed Forces member is just doing their job
AND
IF the Armed Forces member ships switchblades across state lines as part of their job
THEN
the $2,000 fine and 5 years in jail penalties do not apply.
No where does the law say that if you are in the Armed Forces or law enforcement you can buy a switchblade. The law NEVER says ANYTHING about BUYING switchblades.
The law simply says
No one can "SELL/SHIP/Manufacture to introduce" switchblades across state lines,
but if they do,
and they fall into 1 of the 4 exceptions categories,
then they don't go to jail and they don't pay a fine..
So if you lie about being a LEO or being in the military when you try to buy a switchblade you are not breaking any Federal laws dealing with the PURCHASE of switchblades.
Someone with a burr up their hiney MIGHT think you're guilty of "impersonating a LEO" or "impersonating a member of the Armed Forces", but that's a whole nother kettle of fish.