Eurostar trains include both TGV and Siemens Velaro rolling stock.
Is it possible they crammed more seats into the same carriages?
Yes, they do. The old Eurostars (e300) are the Alstom TGV TMST, and the new ones (e320) are the Siemens Velaro.
The e320 have an interior configuration very similar to the ICE-3s in Germany, although I believe that the seat pitch in the Eurostar is shorter than in the ICE.
The same is true for the e300s: they have the same disgusting, sweat-infused seats of the TGVs :)