How to scan a tape in high quality with a stream scanner?

Question

Scanning

Hello! There is a Plustek Smartoffice PS406U scanner. The manufacturer's website says that he can scan at a resolution of 600 dpi. However, in this resolution, the scanner produces images only from an A4 sheet of standard length, but from a tape of the same format, a maximum of 300 dpi, but I would like about 600 dpi, as stated by the manufacturer. Why is that? What software/hardware part introduces this limitation?
I will be glad to any answers. Thank you.