Yeah, seconding posters who said don't worry about the letters too much. Also don't worry about your son not remembering doing anything. I swear it's a BOY THING. My 3 yr old son only has two things to say when I ask him what he did or who he played with at school: "Nothing" and "Nobody"! But then when I pick him up at afterschool and he's in the right mood he'll drag me into the classroom to show me all the works he's learned. So I know he's doing lots of stuff. But good luck getting him to talk about it without pulling fingernails!
The emphasis on practical life works is totally normal. First year in the 3-6 Montessori classrooms is a lot of practical life skills. As others have said, the philosophy is that these skills all build up to making reading, writing, and math easier. This is key to remember, because even if your son is precocious in reading, that doesn't mean the extra time won't ease his transition into formal mathematics. Which can be a real misery for many kids who coast through reading.
Also, I know in our parent teacher talks the teachers discussed the Montessori approach to teaching reading, and emphasized strongly that they don't push it and try to let students come to the "aha! moment of realizing they've figured it out without any public-school-style pushing and formal learning. We are in a highly overeducated town where most Montessori parents are Ivy League professors, so as you can imagine many kids are very precocious. I know I've talked with one parent -- an Italian mom, actually, who knows Montessori from Italy as well as here and is very happy with it -- and one of the things she was most thankful about was that the teachers had really pushed her daughter to do practical life works instead of letting her spend all her time doing math works, which she wanted to do (big surprise!) because both dad and mom are mathematicians and that's all she ever hears about at home. So again, that's a kid who's clearly ready to do advanced mathematics modules - but her parents like Montessori precisely because it's pushing her to do things that aren't in her comfort zone and don't come naturally.
What you mention about your son cutting up in class an being "too social" is really important too. One of the real strong suits of Montessori is that they lay the basic foundation for overall learning without the kind of harsh "stay in your desk" discipline of public schools. I've seen it really work with the older kids in my son's school. The result is very self-directed kids who accomplish a lot because they truly know how to organize their own time without an adult standing over them and micromanaging. It sounds like your son's teachers are doing exactly the right thing for this stage in your son's education: focusing on getting him to self-motivate and self-calm so that he can maintain concentration in the classroom. That will stand him in much better stead in the long run than learning his letters a little faster. As someone pointed out above, there is really not much correlation between how early kids learn to read and how well they do academically in the long run. There's a much better correlation with focus, self-control, and self-motivation -- and those things are what the first year of Montessori is all about.
Anyway, I know that rambled a lot. My son's off school today so I'm typing with a toddler climbing on me and exploring all the wonders of mom's office (eek!) But basically, it sounds like your kid is getting a classic Montessori experience. It may seem "non-academic" compared to public school, and sometimes it's worrying to wonder what exactly they're doing all day. But the Montessori approach has really proven itself over the course of many years in many schools. Obviously you need to be aware of what's happening in the classroom and make sure the dynamic is positive. But if your teachers are licensed, experienced Montessori teachers I don't think you have to worry about their stunting his learning or not "letting" him do things he's ready for. That would be really atypical. And if he's like most kids in that system he'll put it together at his own pace and enjoy the experience.