No it didn't. I've never heard this claim a single time about 5e from any playtester, that the characters are too fragile and so they do more pre-combat tactics.
Er, I guess you don't read RPG.net, then? It's been mentioned a number of times there.
Plus, in the playtests I did, back in the day, when PCs had MORE HP than they do now, and got them back more easily, it was definitely an issue. One PC nearly got one-shot immediately, and generally I saw a great deal more pre-combat prep and attempts to stop monsters even acting. I've also read people on these very boards being happy that 5E encourages more pre-combat prep and less "JUST KICK THE DOOR!", so it's odd that you haven't seen that.
However I am contrasting 4E and 5E. If you contrast 3E and 5E, you will find a different thing. 3E strongly encouraged prep, with long-duration buffs and the ol' "Dump yer spells and rest!" deal. 5E discourages both of those with no long-duration buffs and hard limits on how often you can rest, and a smaller number of spells to buff aaaaand (nearly out of breath) the conc limit of 1 conc spell!
So what I saw was a different kind of prep to 3E - it was more "what can we do to minimize our risk?" rather than "cast a bunch of OP buffs, butcher, and sleep!". You did see that sometimes in 3E and 4E too, but it seems to be more common in 5E, based on my actual playtesting.
Obviously as we've discussed I didn't get to test the latest versions, but the rules changes seem to have made it harder to recover HP and to lower base HP, unless I've misread, from the earlier versions.
You can go from start to finish in 5e combat much faster than in 3e or 4e combat. That's very consistently the report from the playtest reports, and my own experience over the past 10 months. With no additional pre-combat tactics involved.
And this isn't theory, and you don't even have to take my word for it. Watch one of the Slavers live-game videos, and you will see they go through a lot more combats real-time than anyone did with 3e or 4e.
I definitely agree with this - even with way more pre-combat prep, you get through more actual combats in 5E.
The one question I would ask, and this is an honest question, I don't have a strong idea as to the answer, is, how many of those combats are the equal of normal 4E combats in terms of how much they "matter"? I think most are a fraction of a 4E combat in terms of resource-uses and risk.
That's not a bad thing! I like that in a lot of ways. But it is a thing. It's not like with like. It DOES "feel more D&D", for better or worse, to me, though (than 4E), so there's that.
TLDR: I saw way more prep but not enough to significantly slow down the game - it still runs more like 2E speed than 3E or 4E.