I received the same RFE, and it had quite a bit of requests. Such as attach all W-2's, 1099s, and then the actual 1040 filed, along with saying that i didn't meet the poverty guidelines. Then in another section it said even through my income was sufficient, that i didn't show proof of income like last 6 months of paystubs, which would conflict with the failure to meet the poverty guideline language . I think most of the language on the RFE is boiler template, even though it may not apply to you. I was well over the poverty guidelines so definitely not the problem. I know that i sent in my 2017 transcripts with the AOS filing, so I know they just really wanted the most current tax return.
I basically responded with the following, i know it was overkill but better not to have another RFE come back:
1 2018 W2
2 2018 Federal income tax return
3 2018 Income tax transcript (easily obtained from IRS website)
4 12 months of bank statements, brokerage accounts etc.
5 Last 6 months of paystubs
6 Letter from my employer
I think i just threw everything in there just to be safe