I'm not sure I understand this question - you can have multiple Function Blocks on a group - each representing a MIDI 1.0 port?

Page 40. 

MIDI 1.0
If the Function Block represents a MIDI 1.0 Port, then declare it here. If this is a MIDI 1.0 Port, then Number of
Groups Spanned shall be 1.
0x00 – Not MIDI 1.0
0x01 – Yes - Don't restrict Bandwidth
0x02 – Yes - Restrict Bandwidth to 31.25Kbps
0x03 – Reserved

I guess you are taking the mentioned number differently. "The Number of Groups Spanned" is not the number of MIDI 1.0 ports. The number of spanned groups is like, if you have group 2, 3, and 4 for one MIDI port function block, then it is 3.

Since MIDI 1.0 device only had 16 channels, it does not make sense for MIDI1 ports to span the groups beyond 1.

I understand that its the group that are the "ports" . Example, first group =2, spanned = 1, the FB uses group 2.

it could be argued that for MIDI 2.0 it could  cover multiple legacy ports.

For example a hardware device exposing 16 legacy ports and a separate MIDI 2.0 port for another function will need 16+1= 17 FB, at least.

A UMP endpoint does cover multiple legacy ports (most of real world MIDI 1.0 devices would have at least one input and one output).

Note that one Function Block Info Notification represents the information for one FB. You can send Function Block Discovery Message for each function block (specifying respective "function block #" for each) or just send one (specifying "function block #" as 0xFF), as explained at Page 39 (M2-104-UM_v1-1-1), then a number of Function Block Info Notification messages will be returned (one represents one FB, for each).

You can have 17 function blocks (it is up to 32, 00-1F as explicitly stated at Page 40). You cannot just have 33 FBs with 16 inputs and 16 outputs with additional MIDI 2.0 ports. I don't think MIDI 2.0 should cover that many ports though.