Depends on how you read the law and how it is interpreted and any test cases that exist.
That said, the VCRA is very clear on what constitutes an imitation firearm and what constitutes a realistic imitation firearm;
VCRA 2006, Sec 38(1) defines a "realistic imitation firearm" as:
( a ) has an appearance that is so realistic as to make it indistinguishable, for all practical purposes, from a real firearm; and
( b ) is neither a de-activated firearm nor itself an antique
"Imitation firearm" is discussed in Sec38(2) and (3) as below:
(2)For the purposes of this section, an imitation firearm is not (except by virtue of subsection (3)( b ) to be regarded as distinguishable from a real firearm for any practical purpose if it could be so distinguished only—
(a)by an expert;
(b)on a close examination; or
©as a result of an attempt to load or to fire it.
(3)In determining for the purposes of this section whether an imitation firearm is distinguishable from a real firearm—
(a)the matters that must be taken into account include any differences between the size, shape and principal colour of the imitation firearm and the size, shape and colour in which the real firearm is manufactured; and
(b)the imitation is to be regarded as distinguishable if its size, shape or principal colour is unrealistic for a real firearm.
Air pistols may be covered under different legislation but if it can be proved that an air pistol falls under the above criteria it could be argued that it is, by definition, a realistic imitation firearm. For example, the air pistols on this page ( http://www.wonderlandmodels.com/bb-air-guns/air-guns/pistols/umarex/walther/ ) do they fit the definition of a RIF under the VCRA Sec 38(1) (a) and ( b )? I would argue yes they do, as they has an appearance that is so realistic as to make it indistinguishable, for all practical purposes, from a real firearm and they are neither a de-activated firearm nor antiques.
The law has many areas that overlap and at times appear to contradict each other, and it is all down to interpretation and knowledge of all the relevant aspects of the law.
A retailer like the one discussed might view airsoft weapons as 'toys' and may not be aware of the VCRA or even the Firearms Act (although not having knowledge of the law is no defence if an offence has been committed)
(PS - I am not an expert on the law... just find the twists and turns quite interesting )