However, those of us, including myself, you have already brought there family members to the UK, had to meet the previous requirements of £18,500.
The visa at that time is not permanent residency. After 2.5 years, we have to do an Further Leave to Remain (FLR) and after another 2.5 years the Indefinte Leave to Remain (ILR).
At each of those stages the income threshold applies. I see no comment from the government that the increase from 18,500 to 38,700 will NOT apply in these stages, and everyone is only focusing on new immigrants.
As the comment does say, "not retrospective, but it would apply to renewals in the future". Therefore a foreign spouse can already be in the UK, but now has to meet higher requirements in order to stay.
So, as my point was, the difference is that the foreign spouse can use the UK partners income together as a joint income, but for anyone retired or on "low" income, that is going to be a major problem.