Ok, I did, and here is the response:
D&D rule "fact" is an elusive thing. The reality is yes, on page 173 it says "A creature can voluntarily forego a saving throw and willingly accept a spell's result. PHP p 173". 100% correct. However, as a byline of saving throws and we tell you this because it simply is how saving throws work, is that in all reality a player can voluntarily drop their save. However, the player should be informed what spell they are dropping the save for truthfully. So if someone touches them and they believe its a heal in character, that player should then be informed "Actually you are being affected by Slay Living. Do you wish to save?"
This is not a game of out of character deception. However, Rules Interpretations allows for DMs to interpret the rules how they like. A particular sadistic or tough DM may opt to not give the player that choice and simply have them die. As we interpret that rule however, a player is allowed a truthful decision about if they wish to save against a spell or not regardless if they are "duped" in character.
Truthful interactions with players during IC deceptions also fosters good feelings of trust among a gaming group. If a DM is simply out to slay PCs and show how clever they can be by deceiving players out of character, then likely those players may somehow feel that the decision was unfair. As a policy we encourage DMs to have fun with their players and challenge them. However, we do not encourage OOC trickery.
Besides, if you want to get truly technical, Cure Wounds spells do not HAVE saves. So when someone is touched with a cure wounds they will not even be asked to make a save so they will be asked nothing. However, when Slay Living comes into play, they will have to be asked if they wish to save. Dropping your saving throw applies only to a specific spell each individual time. Not that you drop it for a specified period, etc.