I cannot see that paragraph you quoted in the gov.uk link.
BA is not suggesting it is due to the UK immigration policy, they would have consulted UK Immigration on the requirements for entering Israel, which you did not meet.
Thank you for pointing out the KVS availability tool! It seems that the BA customer service representative may have misspoke when suggesting it was UK Immigration.
The paragraph I quoted was in the US State Department:
http://travel.state.gov/travel/cis_p.../cis_1064.html Under "Entering Israel".
It seems that there is conflicting information on the State Department's web site.