It is not particularly important in Feng Shui that the headboard of the bed is a little larger than the bed, but it has some effects in actual use.
First of all, if the headboard is larger than the bed, it may affect the layout of the bedroom. If the bed head is too large, it may take up more space and make the bedroom look crowded.
Secondly, the headboard of the bed is larger than the bed, which may affect the quality of sleep. If the bed head is too large, it will leave a lot of gaps on both sides of the bed, which will reduce the stability of the bed and lead to poor sleep quality.
In short, making the headboard larger than the bed may have some impact in actual use, but there are no special regulations in Feng Shui. If you are particular about Feng Shui, it is recommended that you consult a professional Feng Shui master.