Entering the UK as a visitor (then leaving) before the start date of a Tier 4 visa

I’ve seen some similar posts regarding entering the UK as a visitor then re-entering, but I haven’t seen any ones from recent and thought I’d ask since I’m in a situation like it now. I am a US citizen and have been approved for my Tier 4 Student Visa, it’s currently in my passport. The start date is August 17th, however I am planning on coming to the UK on August 5th as a TOURIST to drop my luggage into my new home, say hi to some family who are touring, and see my partner before he leaves for work. I have tickets to visit to Berlin a week after my arrival on the 5th, returning on the 17th to start my student visa. I plan to show these tickets to the Immigration officer and use this explanation.

Is it still the case that this is technically OK but just a bit of chance on the part of the IO? What are the chances that I would denied entry? Should I cancel all these plans? Thanks.