It's probably a conversion to increase maximum permissible weight of the van and also reduce some weight. Certain upfits (like reefer or car flatbed) are either heavy or require a high load capacity. The regular 3,5t vans with those upfits have a low load capacity of anywhere between 700-300kg. VW Transporter is a slightly lighter than them. With some modifications to the frame (like that one you see on the picture) it can have a load capacity up to 1500kg! I've spotted a similar van in Switzerland: link
It's probably a conversion to increase maximum permissible weight of the van and also reduce some weight. Certain upfits (like reefer or car flatbed) are either heavy or require a high load capacity. The regular 3,5t vans with those upfits have a low load capacity of anywhere between 700-300kg. VW Transporter is a slightly lighter than them. With some modifications to the frame (like that one you see on the picture) it can have a load capacity up to 1500kg! I've spotted a similar van in Switzerland: link