Traditionally, a synthetic stock option involves buying a call and writing a put at the same strike price. I recently encountered an ETF prospectus that claims to achieve this exposure with a four leg trade which I do not understand.
Background: The prospectus for the PJUL ETF (pages 13-14) indicates that the ETF invests its funds in three separate "layers" of options trades. My interest is in the first layer. The prospectus says this first layer is a 4 leg trade that they claim achieves, when considered in isolation, 100% long exposure to the S&P 500. They indicate that the the layer/trade involves (a) buying a European style call and (b) writing a European style put both with a strike at 60% of the current S&P 500 price; while also (c) buying a put and (d) writing a call both at 120% the current S&P 500 price. As pointed out in a comment below, they do not appear to state the relative sizes of these legs (a) - (d), so they might not hold the same number of options for each leg.
Why would they do this trade instead of the traditional 2 leg synthetic stock strategy?