"There must be a reason for it !" ......

Here goes ! ......
LED Vehicle lighting technology is still evolving, and there are MANY variants
advertised as being "equivalent" - e.g. "H4 Equivalent".
The reason behind
why LED equivalent bulbs are not "Road Legal" when used in
a Headlamp originally designed to be fitted with, for example, an "H4" Tungsten Halogen bulb,
requires an appreciation of Headlamp and Bulb design and certification.
The Trophy has "H4" Tungsten Halogen bulbs fitted.
"H4" are a common and standardised type of twin filament Headlamp bulb.
They are often marked to indicate they comply with a certain standard,
e.g. "CE" ( European Conformity ).
H4 "CE" certified bulbs have been manufactured to a certain standard, to ensure consistency
in their manufacture and light output. One aspect of the design is the precise positioning of the two
Tungsten Halogen filaments. ( One for "Dipped" Beam, and one for "Main" Beam ).
Similarly, Headlamp Units into which the Bulbs are fitted have been designed, tested and certified
for use with a specific type of bulb - such as the "H4" and will be marked as such.
The design of the Headlamp Unit and Reflector ensures that a consistent Beam Pattern is produced,
complying with various Reulations - when used with the certified bulb type.
That precise positioning of the Bulb filament, in conjunction with the Reflector
and Lensing design is what produces the specific Beam Pattern.
You may have noticed, if you have ever fitted a Headlamp bulb incorrectly,
that the position only needs to be just a little out, to have a drastic effect on the Beam pattern.
The problem(s) with LED Bulbs, is that there are many different variants - claiming to be,
for example, "H4 equivalent". What this actually means is that an LED Bulb has been built
onto an H4 base, so that it will physically fit into the Headlamp Unit.
The actual LED's of the bulb, and there may be many of them, are not precislely positioned
with the LED(s) in exactly the same position, or are not restricted to only occupy the same position,
as is occupied by the certified / standardised H4 Tungsten Halogen bulb filaments.
The slightly different size / positioning of the LED's can result in the Headlamp Unit
Reflector /Lensing producing a Beam Pattern that does not comply with Regulations,
and that could be dazzling to other motorists.
Until such a time that LED headlamp bulb technology evolves further,
and manufacturers work together to produce an LED equivalent bulb to a common standard,
that can be tested and certified as an acceptable ( to the Authorities ) "equivalent",
then they will not ( at least in the UK ) ever be Road Legal, when used in a Headlamp Unit
designed to be fitted with Tungsten Halogen bulbs.
New vehicles ARE now being fitted - legally - with LED Headlamps - where the Headlamp Unit
AND the LED bulb have been been designed, tested and certified for use
with each other.
