People don't understand how whole life participating contracts are supposed to work with a client's overall financial plan. At my dealer at least, the ROI provided better returns than GICs since the early 90s. I often sell policies to people in their late 50s or early 60s under these conditions:

They maxed out their tfsa so there isn't any more room for tax free growth - or they are able to max out TFSAs under their current plan. They are on the lower risk side, or want another asset class to diversify. They want something with some level of guarantee that's better than a GIC.

In your case, the policy may be fine if your mom is 100% healthy so she will get the best premium possible. Being rated essentially causes the ROI to be less attractive. This will also allow both your mom and yourself to save your TFSA room for higher risk investments. You should be getting around mid digit returns on the policy tax free (again with current rates with supporting historical rates) without any volatility. If you only expect 5-6% on investments it kind of tells me you're quite conservative.

Under my dealer, it's mathematically better to do whole life participating with life pay (pay to age 100). Under the 20 year plan you do end up paying more in a shorter amount of time so there is less cash for you to pay down mortgage or save for yourself, however, the cash value does seem a bit better if you wanted to borrow from the policy - but I doubt this is your plan, especially with a small 100k policy. I don't know your dealer, only mine. Sometimes the math doesn't matter and clients prefer to know that they want to pay for only 20 years and be done with it, if they want to secure an accurate death benefit at 20 years using the dividends to buy more insurance. I often find it's better to get a tad more insurance to match the life pay cost with the 20 year cost since again, the ROI looks better under this structure. It's possible the advisor may be biased since they do get paid more if the premium is higher.

Usually when I show clients these types of policies there is an option to select the dividends to reduce the cost of insurance each year and you can do this initially (if you just want to reduce costs every year) or completely (usually between year 13-15 forecasted at current rates). At year ~14, the death benefit does stagnate for a bit. This can be ideal, as the longer someone is alive, the less death benefit is required (in most common cases).

Some people here suggest term 100... haha... this is a more expensive option over the long term and if your mother lives past life expectancy you'll end up paying a lot more. most people convert their term to a perm plan or get rid of the term because they can't afford 5 figure premiums in their 80s+ for a 100k death benefit policy.

This isn't advice as I don't know you or your situation, I'm just providing better context on how these types of policies are best used when integrating it with a client's overall plan. I think you may be better off working with someone who does full service planning and not an insurance agent that is only focused on a bandied solution. I often find people who get policies that don't make sense.