Those figures relate to general immigration, which wouldn't be affected by ID schemes since people are given approval by the government to arrive and work in the UK. If the government wanted to reduce regular immigration, it could just decide to award less visas.

The ID scheme would only affect irregular immigration which is much lower (approx 50,000 a year by the governments stats, obviously hard to know how accurate that is, but much lower than 1 million[0]).

[0] https://www.gov.uk/government/statistics/immigration-system-...