Agreed. As things stand, as services are commonly delivered, FTTC/VDSL2 and G.FAST are asymmetric in that their upstream and downstream speeds are different, no?
As commonly delivered however all have symmetrical capability.
ADSL is a type of DSL. As is VDSL. As is G.fast. All from the same lineage.
ADSL cannot be symmetrical. VDSL can be through frequency profiles and G.fast can be just by configuring equal time between upstream and down.
Closer to my experience DoCSIS 1 offers a user a share of one 27(rarely), 38 or 50 Mbit (EuroDOCSIS) channel downstream and one 2.25, 4.5 or 9 Mbit channel upstream, from a choice of up to 6 but more commonly 4 channels.
Total RF consumption 6-8 MHz downstream, 3.2 MHz fro. a single modem.
DoCSIS 2 same downstream, upstreams up to 27 Mbit but still only one at once. Downstream unchanged, upstream to 6.4 MHz width with higher order modulations.
DoCSIS 3 - up to 32 downstream channels of 38 or 50 Mbit combined, up to 8 upstreams bonded of up to 27 Mbit each. 32 channels in the UK = 256 MHz of RF. The upstreams in UK 4-6 bonded 6.4 MHz wide channels, 25.6-38.4 MHz. Some bond 8, so 51.2 MHz.
DoCSIS 3.1 - As 3 + 2 * 192 MHz OFDMA delivering 5 Gbit. Also 2 upstream OFDMA channels of up to 96 MHz each, very dependent on how clean the cable network is but 2 Gbit/s of capacity upstream isn't unfeasible.
Fully loading it you're talking a single modem accessing 256 MHz of 3.0 SC-QAM, 1.6Gbit, and bonding that with 384 MHz of OFDM, delivering pre-overheads, while the others mentioned these, 4608 Mbps. Lop 10% for overheads say 5.7 Gbit/s to a single device is feasible. Upstream 2 96 MHz channels would have to partially overlap with the SC-QAM but best case that would run in a mixed mode and 1.5 Gbit is feasible.
4 versions of DoCSIS. Don't think we could call 3.1 a type of 1.0 even though both use SC-QAM carriers still.