Do we qualify for ESA ?

I'm trying to get my head around the ESA NI rules, my partner has been ill the past few years and has had to give up work and is now on the higher rate for both elements of PIP. We never considered applying for ESA as we thought it was an income based benefit (I'm working so would not qualify if it was).

Now we are worried we have left it to late and his NI record is to far in the past, however we were reading this.

"you’ve paid at least 26 weeks class 1 or class 2 National Insurance (NI) contributions in one of the last 2 complete tax years and have been paid or credited with NI contributions for at least 50 weeks in each of the last 2 complete tax years. The 2 tax years must be the ones that were completed before the benefit year in which your period of limited capability for work began. The benefit year runs from the first Sunday in January. The tax year runs from 6 April to 5 April. You can check your national insurance record online or call HMRC's helpline on 0300 200 3500 if you’re not sure."

His NI record is as follows.

Current tax year=£0
17-18=Partial (Below LEL)
16-17=Full
15-16=Full

Now on reading the above advice from the CAB it says "The 2 tax years must be the ones that were completed before the benefit year in which your period of limited capability for work began."

Am I reading this correctly that the current benefit year started in Jan 18 and thus the tax year 17-18 is ignored (as it ran to April) and the rules about the two tax years relate to the tax years "15-16" & "16-17"