Concerns about my 2.5 year old nephew (autism)

Obviously this is not my own child so I don't have a full picture as it were, but I generally see him every week for an hour or two (if not more). For a while, I've had concerns but I don't know if it's unfounded or not. Could those with experience give me any extra insight on what I've noticed with my 2yo nephew (turns 3 end sept.)

1. Generally lines toys up (farm animals, building bricks etc.) I bought a hoop toss game for Easter and his wasn't interested in doing anything but line all of the different pieces up no matter how much his mum or I encouraged him and demonstrated how to play properly with my 2yo son who's 2 months older.

2. I've noticed he still walks on his tiptoes some of the time. I can't say I've noticed it all of the time.

3. His speech seems somewhat behind. He has a great memory and recalls numbers and letters and sings lots of rhymes. I was sent a video of him by his nana who showed him repeating lots of words. This is honestly the most I've seen him speak but it was all parroting. He doesn't apply words generally or speak (lots of it is still baby babble that no one understands). He may say some short phrases 'bye-bye,' 'no auntie' or 'mummy pig' but I haven't heard much of this. He can also names animals and other toys but doesn't ever say more than 2 word-phrases.

4. He apparently has major meltdowns in the supermarket, which I've been told by more than one person on serval occasions. I wonder if it's to do with sensory overload.

5. He doesn't seem to respond to his name when I call it. I tried getting his attention last week to show him a passing train. I called his name serval times but he didn't look up. His parents called another couple and he eventually looked. He didn't follow my finger pointing to show him the train and he was physically turned to show it by his dad.

6. He has some issues socially. He can be over affectionate with other children that he doesn't know (giving them tight hugs when they don't want or trying to kiss) despite them not wanting him to, sometimes causing upset. Or, can go the other way and be rough and snatch toys etc. which has meant my son (again, only 2 and a bit months older) is now very weary of him.

** I will also say that his childcare arrangement is a family member watching him full time so other than playgroups he doesn't have much other interaction with kids.

***His mum's first language isn't English. However, I'm pretty sure that's all they speak at home as dad is English and only speaks this.

So my questions are, do you think this is concerning/ a sign he's autistic? And if you do, what should I do? Keep it to myself? Share my concerns in a caring way?

We're in England so I'm sure the process for S&L and autism referrals will be quite different to other places.