Yes! I kind of like how they save one plum parody role for him per season (last season, since SpiderMonster was the best parody, it meant Frank Grover). It's a nice vocal turn, plus I love the "flappers."
It's unquestionably Frank if you watch the Birdwalk skit (it doesn't sound like Jacobson at all). We don't need a source in this case, it's his contribution for the season (since he is still credited and does still do one to two skits per year, but only that). Some of the others were sourced, but in all of the aforementioned, it's definitely Frank Oz.
Heh, don't forget (or if I never told you, here it is now), I *am* also a contributor to Voicechasers.com (and have been since around 2000 or so, somewhat less frequently outside of general updates in recent years, but I still keep an eye on it, especially when I find info on obscure English dubs of vintage foreign animation, anything with radio actors in it, and radio shows themselves). Some people I still have no ear for as yet (I really wouldn't be able to ID a Leslie Carrara character yet without some closer study, and in some cases outside the Muppets, or even with since some do commercial or video game/cartoon work as well, I pull a demo from Voicebank.net to listen to side by side for comparison). But Oz remains distinctive, especially since he *has* aged, whereas Jacobson's Frank voices, while sometimes a better match than others (his Piggy sounded closer, definitely at times a dead match, than his Fozzie to me), still have a "younger" sound, or a character actor assuming gruffness as opposed to the tone which Frank has, even when just being interviewed as himself. Mr. Tiger is clearly Eric but using a sort of growly version of his Bert or Grover, compared to the Oz roles mentioned (if I had a clip, I'd show you). It's also discussed in the Why doesn't Frank Oz perform with the Muppets anymore? article (which at first, some time back, I thought wasn't needed, but outside of being a good article on its own, it helps answer these questions and actually better make it clear when he *does* work on the show.
That's why, now that the vintage clips have mostly been reserved for the DVDs, online archive and specials, Oz still gets a credit each season and a performer profile on Sesameworkshop.org: "Frank Oz has been a major creative force behind the Muppets™ since 1963. Oz performed Bert, Cookie Monster and Grover for more than 30 years.While Eric Jacobson and David Rudman have taken over the bulk of his character work, Oz still occasionally comes by Sesame Street to perform." A few of our mutual friends (from here or Toughpigs) have also sometimes posted Facebook photos when they happened to run into Frank when he was doing his Sesame spot(s) for the season. Plus, once the Mad Men parody aired (first time Frank had played a new character in ages), we were on the alert for him possibly doing something beyond a Grover or Bert return.