Mind sharing the newer months(Mar-Jun) of IRR? wanna gauge how their returns is like in this situation as compared to their marketed 1.9%.

TIA
Using the same comparison of IRR since 22 Nov 2019 up to end-Apr including that quarterly rebate it was 1.823%. If I compute IRR since end-Jan to end-Apr, it was 1.839%.
I had some cash movements in and out of Simple in May/Jun to park some spare cash, so my actual returns are now affected by timing of the movements and not such a good comparison anymore. Definitely looks lower than previous months so far though. It's also almost end-Jul and time for the next quarterly rebate, where we'll see if they decide to rebate more to "make up" or if they'll finally revise their projections down.
If you just look at the two funds' NAV for 30-Apr till 16-Jul though (LNWELIA, OCBSGDM), it's about 1.51%, though that's obviously before the trailer fees rebate and any transaction fees.
During the Endowus Cash Smart launch webinar, in their comparisons they stated that StashAway Simple had a 1-year historical performance of 1.71%, then moving forwards, gross projected yield of 1.92% and net projected yield of 1.67% (as of 26 June 2020). I've not tried to verify that, since it seems to rely on info from the fund managers that isn't updated so frequently publicly.