A couple of reasons why terminating a standard reusable three pin plug, onto a round 2.5 mm cable is a actively discouraged, is likely to be one of the following.
Termination to the individual pins is difficult with single core conductors purly down to their cross sectional size.
The inside of the plug body can become a little “Busy” when using this size flex.
The cable restraining clamp, can also become over stained and fail if incorrectly installed because of the outside installation of the 2.5mm cable diameter.
One of the biggest safety factors, is the fear that when somebody try’s to attach a 2.5mm cable to a standard three pin plug, they intend to use it incorrectly to run a piece of electrical equipment that will pull a much higher load that a 13 Amp plug has NOT been safely designed to handle without over heating.
The 2.5mm cable can carry the higher intended load for longer periods of time, but the 13 amp plug will become compromised by heat and become unsafe.
Safer to actively discourage this type of practice altogether !.
Back in the day, old school two bar 2kw electric fires where fitted with of a “Of The Shelve” reusable 13 amp rated three pin plug.
People used these fires for hours and hours on end and never gave any though to why the 13 amp plug top became hot
????.
For load carrying capacity, the cable can not be over sized, only undersized.
So, the electrical “Man Math’s” have stated that a 1.5mm cable is suitable to run a “Granny” unit over a given distance, then who Am I to argue ?.
The facts speak for themselves folks !.
We all have / had plastic consumer units installed in our houses, because it was decided that it was the safest material when dealing with electrics inside an enclosure.
Now, guess what !.
They have now changed their minds and we are all recommended to have installed “Metal” conductive consumer units instead, because of collapse due to the risk of fire !.
