1080i5000 Decklink diag spikes

As you can see in the attached screenshots, 1080i5000 causes spikes in ‘frame-time’ (or ‘consume-time’,I’m not sure). Also the ‘line’ isn’t in the middle of the diag row, in 1080p5000 both issues are non-existent. Is this expected behaviour?

I’m running 2.2.0 stable on a Win10 Enterprise, Intel XEON 2136, Quadro P4000, 32GB ECC RAM, 2x Decklink Duo 2 (2x key/fill on card 1, 2x fill-only on card2), Samsung Pro NVME drive.