Most , if not all , of these kits are meant only as tempory fixes (get u home) because they are inserted from the outside the potential is there for them to come loose and be thrown out , particularly if fitted poorly (an lets face it not everyone is good at these things !). A restricted speed would always be wise for the same reason.
Some tyre companies do not even suggest that their tyres can be repaired at all.
Michelin do allow a professional , vulcanised , internal repair depending on its size , position and provided the interior of the tyre has been checked and no other damage has been found.
(Another reason not to just carry on riding with this type of repair).
At the end of the day admittedly its personal choice but some common sense has to be applied to avoid unnecessary risk to oneself and others.