I guess it is down to the individual who picks that particular part of your shopping. I used to do it when I was a student and always used to try to make sensible substitutions where possible and also pick fresh produce with long dates etc. For those who find they get nothing rather than a substitution, I’d hazard a guess that the picker is taking the easy option to avoid going over the allotted time for their section. They have targeted times to pick the shop (not just the fresh produce). Plus the whole order isn’t picked in one go, so they are doing shopping for up to 6 customers in one go so I guess sometimes items get put in the wrong tote etc.
Can’t believe how ridiculous some of the substitutions have been though! Eek