My experience of the HH5A is that it didn't appear to support G.Inp as it synced at a lower speed than either a HH5B or a Huawei HG612.
According to Openreach it does for downstream. I think the lower speeds is probably a result of the lantiq chipset. The others use BCM chipsets.
Ive never used a HH5A, but when using a TDW-9980 which has the same VRX268 chip my speeds can be 5~8Mbps lower... and that's despite me being on an ECI cab.
Says sagemcom on it
Yes, the HH5A is manufactured by Sagemcom -
linkThe HomeHub 5A contains a Lantiq VRX268 chipset (Same as the ECI modem) and manufactured by Sagemcom.