The issue that you mention really depends on how you want to lay the pavers as you have multiple choices. Here is a link to our porcelain installation brochure we are in the process of finalizing which gives the various installation methods/options. Brochure is not quite finished but should have all the info you require.

So basically you can lay them over sand or gravel and fill up the joints with sand or lay then with adhesive/thinset and us a more permanent grout, or lay them over 3/8" or 5/8" high rubber pads and leave the gaps between open.

But if dry laid you can still take them up from time to time to clean under them,