I saw in the "New English File - Advanced" book (p. 139, Unit 2A) from Oxford University the use of "used to" and "would" for past simple and one of the rules says:
"we don't use would with stative verbs, i.e. to talk about situations or states which have changed."
But in an exercise of the same book the correct sentence are:
"Our grandmother would always have a little surprise waiting for us when we visited."
"Our grandmother always used to have a little surprise waiting for us when we visited."
And "have" is a stative verb ... Someone could explain me why is this correct? please