Are there any benefits?
Stimulative feeding is done to try to encourage the queen to lay more eggs, so the colony will build up quicker to take advantage of an early nectar flow, such as oil seed rape. It is an old idea that was advocated long before OSR was grown widely and is in all the older books.
I believe the origin of "thin" syrup, 1lb sugar/pint of water, is that it was used for spring stimulation in the belief it made the bees think it was nectar.
In my early days in beekeeping I practiced stimulative feeding, but I didn't think it always had the effect it should have done. I suspect it works much better on prolific bees, but I found that if the colony had enough stores it would build up well enough on its own.
Although I live in the south of England we can still have frosts until mid-May and bees can go back into semi-cluster. My concern has always been that if the brood nest is stretched, the outer areas of brood will be the ones to suffer. Also, if the ratio of brood is too high compared to the number of nurse bees to look after it, I think there may be a nutrition problem, allowing disease to erupt, chalk brood in particular, but possibly EFB as well.
Michael Bush on his brilliant website has brought together some quotes from well known beekeepers who have been opposed to stimulative feeding. I accept that most of them are American, but they have prolific bees that are likely to gain most benefit from stimulative feeding.