As I already explained, none of that makes it so that you have to "resort" to using Mummy. It's an effective strategy, therefore it's not something you have to "resort" to using.
Whether or not you have another way to get rid of Truant is irrelevant. As I explained, just because you have only one way one way to do something doesn't make it something you have to "resort" to doing.
Resort[rɪˈzɔːt]
1. a place to which many people go for recreation, rest, etc.
2. the use of something as a means, help, or recourse
1 obviously isnt applicable as it means the other meaning of the word, but 2 is the actual definition of a resort, and this most definitely is a resort
a resort says nothing about it being an only option, or about it being bad or ineffective at all, slaking has to resort to mummy as a viable way to remove truant in single matches though, that is the definition of a resort
the way you were acting to M BLADE has come off seeming rather arrogant and ignorant
i personally love this strategy, but it is still something slaking has to resort to to remove truant in singles
as for the strategy itself, it can work, but it is a very one trick pony for slaking since he is left without a choice band to be workable with truant, and desukan forfeits another item for the escape button
if the opponent counters it with a red card on any pokemon get hit by slaking, or any other form of phasing, they will not fall for it again, and you can not get the garunteed mummy pass without the escape button which has been used
EDIT: also, does ditto copy mummy if it copies a mummied pokemon? if so thats another possiblity to stop it like other set ups