PCIE4C blocks for UltraScale+ Devices Integrated Block for PCI Express, use of PCIe gen4 retimer
In the datasheet named "UltraScale+ Devices Integrated Block for PCI Express v1.3 Product Guide Vivado Design Suite PG213 (v1.3) November 18, 2019" there is a table "Table 1: PCI Express Base Spec 4.0 v1.0 Features Supported by PCIE4C" which has a notion about unsupported features of PCIe gen4 for PCIE4C blocks. I am interested in the meaning of line "Link Extension Devices (Retimers) - NO". I have several questions based on this table.
1) Does this mean that no retimer must be placed in line between, for example VCU128 board and a PC?
2) Does this mean that no protocol analyzer (i.e. packet sniffer) must be placed in line?
3) How should i interpret the line in this table "Link Extension Devices (Retimers) - NO"?
4) Can PCIe to U.2 adapter be used to convert PCIe bus to U.2 (so adapter is not actually a retimer)?