Sorry, but I have seen nothing which explains why a would-be abductor would target 5A, what time he went in and why he chose to go in at that time.
I see once again you have refused to answer my question - what makes abduction both illogical and implausible in your view. However, despite this refusal on your part I will answer yours.
Why would an abductor target 5a? Because it was an easy target, ground floor, easy get away and above all unlocked. How many more reasons would you like?
What time did he go in? Can't be certain but a window of opportunity was identified by the Met and I would hazard a guess that that window was some time between 9.30ish and 10pm. Unless you are claiming that the Tapas group was so attentive that there was someone from it in or within the near vicinity of the apartment at all times you would have to allow for the possibility that there were several minutes together when no one was around which would have provided that window of opportunity. Why did he choose the time he did? Well I guess it was because he considered the coast to be clear. Now, what is implausible or illogical about that?