I could not reproduce this on MacOS with 1.5.3. Your ods sheet has the decimal point but my german locale has the ",". If i copy a number like "21.44" then this results in an empty cell in pspp. When I create a new ods sheet with "," and then copy a number like "21,44", then it works. Pasting into pspp has two modes.

a) Just select a cell with one click. Then it works
b) Double click a cell -> This enters the edit mode of the cell and you can type something. If you paste now, then it pastes the number as a string with a trailing space. This results also in an empty pspp cell if you do not remove the trailing space.

c) It even works with copy paste of a whole range of cells e.g. copy 2 x 2 cell range in ods resuts in a correct paste in pspp.

Could you check if the decimal point is the same in pspp and libreoffice?