Hi All,
My build phase started 4 days ago, I haven’t noticed ANY change in the type of workouts being recommended, despite the fact that the focus is now 1/2 of what it was in base…Here’s my question:
Is the system waiting for me to start doing harder efforts before recommending it by itself, despite the fact that are now in the Build phase ??
Thanks
No
The transition just happens gradually during build, so that by the end of build / start of peak you are recommended workouts for your athlete type.
Other relevant questions are
What is current stars count?
What is IR currently set to?
What do you mean by “different”? 
There is a range of potential workouts on any given day/week during each phase dependent on predicted form.
Are you only selecting workouts from top four or do you also use Load More and Filter?
As @wescaine mentions intensity levels will increase by latter half of Build whenever form is fresh. You can also slide freshness feedback slider to the right if predicted form does not match how you feel.
Climber focus is still at the longer end of the spectrum (10 minutes) and as mentioned, it will not shift immediately… there is only one step between 1hr focus and 10 minute focus, and that’s 20 minute focus… and that overall transition is spread over 6 weeks
In the XATA part of the training tab of the website, you can see the current focus duration under the little image showing your program phase… there is also a slider there that shows you how the focus will change week to week… if you move that to the right, you’ll see when the focus starts to change (e.g. changes to 20min power from one week into build… then 10min power after another 4 weeks… and stays there through peak)
Perhaps need a better way to illustrate how this works in the software… It really is a crucial aspect to the software - if the user’s selected athlete type is relatively longer focus type, then there is much less of a shift in recommended workouts, while users with a ‘Power Sprinter’ athlete type would experience the largest shift in workout recommendations from Base to Peak phase.
Load More gives you greater variety to choose from if you are bored with the “TOP” four. 
“TOP” factors in what you did last week on same day XSS-wise. If you have more or less time to train on any particular day, you can use Filter to change the recommendations.
Here’s some examples that I got with similar settings as you, selecting from top four and moving from 2 to 3 stars during Build phase –
–ending Build (TL ~89)
SMART - The Beauty of Suffering
SMART - Takin’ Care of Business - 120
SMART - No Time To Cry - Extended Mix
SMART - Magic Carpet Ride
2hrs endurance
SMART - Somebody Told Me - 120
SMART - Dance with the Devil - 3.5
Endurance Builder 126
SMART - Uprising
SMART - Song 2
Endurance Builder 160
Rub-a-dub-dub 90
Me Dazza
If you say so 60
Iron Man - 120 - SMART Power
CX 2by2’s
Sweet-Spot @82% - Classic 3x20
SMART - Best of You
Lower Threshold Power - 2x 1hr
Take Me To Church
The Time Is Now - 120
SMART - Best of You
Iron Man - 120 - SMART Power
Up & Down LTP
Kick it into the Middle - 90 (RC Version)
SMART - My Own Worst Enemy
Me Dazza
SMART - Takin’ Care of Business - 120
SMART - Lucy in the Sky with Diamonds - 120
SMART Xert Zwift Surplus Seeker 75min
Threshold Builder 6
SMART - Takin’ Care of Business - 90
SMART - Save Yourself - 120
–begin Build (TL ~60)
Peak included –
SMART - Let’s the Sparks Fly
SMART - Ready to Start
SMART - Riders on the Storm 120
SMART - Uprising+
SMART - Hammer to Fall
SMART - Song 2
I didn’t look up each workout profile, but let’s just say there is plenty of variety including HIIT challenges when fresh. 
Weekly pattern for this progression was Mondays off and longest workouts on weekends (Sat or Sun). YMMV