I think this is unlikely: fpGUI has a long history even before Graeme started to work on it. Its roots go back to the KCL being developed in 1999/2000 (?).
IIRC KCL (and Kassandra the IDE) was more VCL/LCL like. Sebastian then wanted something he could bring quicker to market and was frustrated with time that it took to do somewhat useful VCL emulation and first created fpgtk. Later he generalized that a bit and added windows support and that became fpgui. That was 2000-2001 I think and kcl-kassandra before 2000.
After 2003-2004 (win32 port was added by Micha in that period) he thought Lazarus was making good progress and dropped maintaining the fp* stuff. I don't know if fpde has been used for the main docs by Michael, or only for other projects.
fpgtk is still in the FPC tree because it was used for a few GUI utils in the FPC tree, like FPDE, the fpdoc editor. Hasn't seen any action except minimal changes to keep them running. FPDE is still in utils/fpdoc/fpde. I'm not sure if there is a package still using it, a doc editor has been integrated with Lazarus now.