I think you are correct. I tried using one of the FritzBoxes without my Zen credentials and no interwebs! Is there really no way of seeing the current DSL connection speed and other exciting data the FritzBox provides on the ECI? Is it really just a dumb modem?
Not without some kind of hack to the unit (I'm not even 100% sure there was a hack for the ECI). forum.kitz.co.uk is probably the best site to find out about that.
If you want an out-of-box VDSL modem that you can get lots of stats out of, you can use a Draytek Vigor V130. It has basic info on the web interface, and a lot more detailed info via an ssh interface.
For advanced use it can also I believe (I haven't set one up like this) act as a PPPoE client - and when used like this it bridges the public IP onto the LAN interface for a router to connect to without having to do PPPoE itself. That may mean the router loses the PPPoE overhead.
I know you said "don't ask", but not really sure what the benefit is that you are trying to extract using an external modem, particularly if the Fritz has the kind of info you need. Most of the time you'd use an external modem to act as a modem because you needed it to use a particular router which otherwise couldn't connect to the incoming service.
Following is an example of the command like stats I can get from my Vigor 130:
vdsl status
---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
Running Mode : 17A State : SHOWTIME
DS Actual Rate : 79995000 bps US Actual Rate : 20000000 bps
DS Attainable Rate : 92278328 bps US Attainable Rate : 25681007 bps
DS Path Mode : Fast US Path Mode : Fast
DS Interleave Depth : 1 US Interleave Depth : 1
NE Current Attenuation : 10 dB Cur SNR Margin : 4 dB
DS actual PSD : -2.-9 dB US actual PSD : -2.-7 dB
NE CRC Count : 0 FE CRC Count : 1505
NE ES Count : 0 FE ES Count : 1287
Xdsl Reset Times : 0 Xdsl Link Times : 13
ITU Version[0] : fe004452 ITU Version[1] : 41590000
VDSL Firmware Version : 05-07-06-0D-01-07 [with Vectoring support]
Power Management Mode : DSL_G997_PMS_L0
Test Mode : DISABLE
-------------------------------- ATU-C Info ---------------------------------
Far Current Attenuation : 7 dB Far SNR Margin : 9 dB
CO ITU Version[0] : b5004946 CO ITU Version[1] : 544eb206
DSLAM CHIPSET VENDOR : < IFTN >
> vdsl status more
vdsl status more
---------------------- ATU-R Info (hw: annex A, f/w: annex A/B/C) -----------
Near End Far End Note
Trellis : 1 1
Bitswap : 0 0
ReTxEnable : 0 0
VirtualNoise : 0 0
20BitSupport : 0 0
LatencyPath : 0 0
LOS : 2 0
LOF : 0 0
LPR : 0 0
LOM : 0 0
SosSuccess : 0 0
NCD : 0 0
LCD : 0 0
FECS : 0 26313 (seconds)
ES : 0 1287 (seconds)
SES : 0 13 (seconds)
LOSS : 0 61 (seconds)
UAS : 40 437 (seconds)
HECError : 0 0
CRC : 0 1505
RsCorrection : 0 0
INP : 0 0 (symbols)
InterleaveDelay : 0 0 (1/100 ms)
NFEC : 255 255
RFEC : 16 16
LSYMB : 5410 21451
INTLVBLOCK : 255 255
AELEM : 0 ----