A law enforcement officer does not know every law and would not likely have learned what makes a stop sign comply with the law as an official traffic control device. Go back to your friend and ask them what are the requirements listed in statues that define an official traffic control device.
Here are a few. Things mix together to form a big picture. Taken as a collection, they form the basis for what approval needs to be done in order to put up a stop sign, its size, the location it must be placed, and the requirement for being an official sign in the traffic laws.
The undersized stop sign, placed without approval, in an invalid location, on the wrong side of the road, below the required height... is not an official traffic control device, and therefore is not legal as the basis of LEO giving out tickets. Hence they are a "suggestion" only.
Chapter 316 - 2012 Florida Statutes - The Florida Senate
316.008 Powers of local authorities.—
(3) No local authority shall erect or maintain any official traffic control device at any location so as to regulate the traffic on any state road unless approval in writing has first been obtained from the Department of Transportation.
316.077 Display of unauthorized signs, signals or markings.—
(1) No person shall place, maintain or display upon or in view of any highway any unauthorized sign, signal, marking or device which purports to be or is an imitation of or resembles an official traffic control device or railroad sign or signal, or which attempts to direct the movement of traffic, or which hides from view or interferes with the effectiveness of any official traffic control device or any railroad sign or signal.
316.1945 Stopping, standing, or parking prohibited in specified places.—
(1) Except when necessary to avoid conflict with other traffic, or in compliance with law or the directions of a police officer or official traffic control device, no person shall:
(a) Stop, stand, or park a vehicle:
3. Within an intersection.
316.0745 Uniform signals and devices.—
(3) All official traffic control signals or official traffic control devices purchased and installed in this state by any public body or official shall conform with the manual and specifications published by the Department of Transportation pursuant to subsection (2).
https://fdotwww.blob.core.windows.ne...vrsn=425f8ce_6
See section 2.39 defines sign size minimums for legal traffic control signs. (much larger than 12")
Very simple overview summary guide for meeting legal standards:
Stop Sign MUTCD Regulations - Universal Signs & Accessories